About merchant ship wartime colours

[Mister_M]

Originally Posted by gap

The last picture seem original though, but all the portrayed ships look to me as being plain grey, except for the vessels on the center left - probably an auxiliary vessel - which sports a dazzle pattern.

They are all grey with camo skin ("dazzle").

Originally Posted by gap

It is hard to say from this picture as shadows might milead our eyes, but yes, several ships in the picture above seem to have black hulls and bright supestructures.

Perhaps a slow convoy with old steam ships still burning coal (they have a stern of the old type), small ships of less value which are not worth to camouflage with grey paint...

https://www.history.navy.mil/content...1772365144.jpg (from here : https://www.history.navy.mil/researc...ip-shapes.html)

[gap]

Originally Posted by Mister_M

They are all grey with camo skin ("dazzle").

It is my impression that dazzle camoufflages were only used on naval and auxiliary vessels, or at least I have never seen a merchant ship in complex camo scheme. To me, only the ship on the right has a dazzle pattern painted on her hull and I suspect her to be an auxiliary, but again my eyes are not very sharp

Originally Posted by Mister_M

Perhaps a slow convoy with old steam ships still burning coal (they have a stern of the old type), small ships of less value which are not worth to camouflage with grey paint...

https://www.history.navy.mil/content...1772365144.jpg (from here : https://www.history.navy.mil/researc...ip-shapes.html)

Yes, from their look those are definitely not "modern" freighters. As for them not being worth a dozen cans of grey paint, well, according to one of the posters in the forum thread I linked at post #1, a decent grey coat could be obtained by mixing black and white paint, which for sure wasn't in short supply at that time

[kapuhy]

Originally Posted by Mister_M

Perhaps a slow convoy with old steam ships still burning coal (they have a stern of the old type), small ships of less value which are not worth to camouflage with grey paint...

I doubt cost of paint would be a consideration compared to any ship's value, (especially since paint needed was probably already on board - as noted in gap's link, all they needed is to mix black and white paint they probably had stored since these were most common colours during peace) but with ships operating in low risk areas their captains could indeed decide the risk is too small to warrant the time and effort needed to repaint them.

Edit: ninja'd

Some other findings:

- German supply ship Roda sinking after being torpedoed in 1940. Interesting example of keeping black/white painting and funnel colours even after being taken into navy service:

https://shipwrecks.com/wp-content/up...da_sinking.jpg

As for rules for peace-painted ships and coal burners in convoys, there were obviously exceptions, as shown by photo here (atlantic convoy in 1941, phot taken by Robert Capa):

[Mister_M]

Originally Posted by gap

... black and white paint, which for sure wasn't in short supply at that time

This is just your opinion.

Originally Posted by kapuhy

I doubt cost of paint would be a consideration compared to any ship's value, (especially since paint needed was probably already on board - as noted in gap's link, all they needed is to mix black and white paint they probably had stored since these were most common colours during peace) but with ships operating in low risk areas their captains could indeed decide the risk is too small to warrant the time and effort needed to repaint them.

In real life, I don't know how much time it was needed to repaint a whole ship. Maybe lack of time ? Lack of crew ? Lack of equipment (in wartime, all is restrained) ? Lack of... money (and you will have to repaint again the ship after the war) ?... Or even other things that we just cannot have an idea or we just cannot imagine...

Originally Posted by kapuhy

As for rules for peace-painted ships and coal burners in convoys, there were obviously exceptions, as shown by photo here (atlantic convoy in 1941, phot taken by Robert Capa):

One photo cannot say anything about the whole story.

Maybe coal burners were not repainted grey because it was totally useless to try to camouflage a ship which produces so much black smoke !...

[gap]

Originally Posted by Mister_M

This is just your opinion.

Not exactly my own opinion:

Its common sense and natural to use camouflage John.
All ships use more black and white paint than any other colour so a mixture of these would soon produce grey in an emergency.
I was at sea from 1936 to 1956.

https://www.shipsnostalgia.com/threa...1/#post-356479

Originally Posted by Mister_M

In real life, I don't know how much time it was needed to repaint a whole ship. Maybe lack of time ? Lack of crew ? Lack of equipment (in wartime, all is restrained) ? Lack of... money (and you will have to repaint again the ship after the war) ?... Or even other things that we just cannot have an idea or we just cannot imagine...

I don't think the factors you are mentioning could affect big shipping companies, but indeed they might have played a role for small shipowners

One photo cannot say anything about the whole story.

Originally Posted by Mister_M

Maybe coal burners were not repainted grey because it was totally useless to try to camouflage a ship which produces so much black smoke !...

Maybe, but again:

I was a seaman all through the war and sailed in many convoys.Convoy Commodores were very strict and would reprimand any masters of ships who had bright colours visible,as occasionally some ships had red lead showing.
Emitting smoke from funnels was also taboo.

https://www.shipsnostalgia.com/threa...1/#post-357900

As noted by kapuhy, brightly painted ships and old coal-burning tramps sailing within convoys might have been not too an uncommon exception to the above rules, but I would expect them to become rarer and rarer as the war progresses.

By the way of that amazing picture by Robert Capa I think I have found the full set of photographs:

https://www.lasegundaguerra.com/viewtopic.php?t=13661
https://izismile.com/2017/06/01/a_tr...1_32_pics.html

Capa documented at least two Atlantic convoys. Apparently this set is from his first crossing, which took place in December 1941.

Please note this other freighter with dark hull, bluff superstructure and white/blue funnel from the same convoy...



...and the bad paintwork on these tankers





@ kapuhy good finding!

[Aktungbby]

Originally Posted by gap

If you have any other information on the subject, be it in form of pictures, documents, first-hand reports or simple impressions, you are welcomed to share them here

https://maritime.org/doc/camo/index.htm

Revised
June, 1942


This publication is CONFIDENTIAL and shall be handled in accordance with the provisions of Article 76, U.S. Navy Regulations. It shall be given a wide circulation among commissioned personnel.

The publication shall be destroyed by burning when no longer required. No report of destruction need be submitted.

<TRANSPORT AP 21 Class
Measure 16 - Thayer System PLATE XI

< PLATE XII - Cargo Ship AK 25 Class - Thayer System 24

INTRODUCTION
Definition of Ship Camouflage
Ship Camouflage may be defined as the means by which the visibility of a ship is reduced, or the means by which deception is caused in course or range estimation, or in class identification.
The most common method of attaining these ends is through some form of special painting, and this book is limited to camouflage by that means.
This is the Second Revision of SHIPS-2, and it supplants all previous issues in their entirety. Further revision should be expected and encouraged in a subject in which practice is far from becoming crystallized, and this book is therefore issued in loose leaf form. It is requested that pertinent comments be submitted and that instances of notably effective and ineffective camouflage be reported. Special forms for making camouflage reports have been printed and are issued with this book.
The Selection of a Suitable System
Ship camouflage measures have two general purposes:
(a) The Reduction of Visibility - Protective Coloration
(b) Course or Range Deception - Generally Pattern Systems
The systems included in this book belong in the first category. though Measure 16 contains some elements of deception.
No one type of camouflage can possibly give any protection under all situations. The method of ship painting must be adapted to the tactical situation which is involved, and a radical change in the tactics of either offense or defense should entail a re-examination of the suitability of the type of camouflage already in use. A method of ship painting which is intended to give protection during a period of greatest danger may at other times be of very high visibility.
Measures for reducing visibility have best chance of success at night, in gray weather or on hazy days when visibility is limited. Very light colored ships are best at night except in the glare of searchlight. Light colored ships are best against periscopic observation and dark ships are best against air observation. When light ships are clearly visible it is easy to judge target angle and make identification. Dark ships are much better in this respect.
The systems presented are to be placed in effect when ordered by competent authority. A summary of conditions under which the various methods will prove most effective is given on page 4, and a fuller explanation will be found under each camouflage measure.
APPROXIMATE EFFECTIVENESS OF CAMOUFLAGE MEASURES
FOR SURFACE SHIPS
Useful for Protection against Submarine attack, where aerial observation is a lesser factor.
(A) In northerly waters with much overcast weather and where attacks are prevalent at night.
Measure 16-Thayer System
Measure 13-Haze Gray System
(B) In Atlantic or Pacific Coastal waters where weather is generally sunny, visibility is high, and bright moonlight is common at night.
Measure 14-Ocean Gray System
Useful where greatest danger is from the air and high surface visibility must be accepted.
Measure 21-Navy Blue System

Useful for combatant ships operating in areas where greatest danger might be expected from gunnery action either from shore batteries or from enemy surface ships. Moderately high visibility to aerial observation at close ranges.
Measure 22-Graded System

MEASURE 16 - THAYER SYSTEM

Effectiveness

Lowest visibility to surface observers on moonless nights and in overcast weather.

High visibility down-sun or down-moon in bright clear weather, but reduced visibility up-sun and up-moon in all weathers.

Especially well adapted for winter use in Northern areas where nights are long and days frequently overcast. It would prove useful against submarines in any area where attacks occur mostly at night, but in bright weather it would be very visible to surface raiders, or to high-flying aircraft, when observed down-sun.

Some deception as to target angle has been reported for both day and night operations.

Special Characteristics

The special feature of this system is its changeable character. At low levels of illumination a blue paint will appear relatively lighter and a red paint will appear relatively darker than these two paints appear in daylight. This visual change, known as the Purkinje effect, is utilized in the Thayer System. The pure light blue which is employed has been selected because it will appear practically like white paint at low levels of illumination. The ship will therefore appear like a white ship on moonless nights or during twilight when white or very light ships are best for reduced visibility. During daylight hours or under bright moonlight the pattern will be apparent and will produce some deception in the estimation of the target angle. A darker blue would produce more deception but can not be used because it will not appear white at night. The purity of the color is an important factor in the Purkinje effect, and even a slight admixture of black in the paint will reduce its effectiveness at night.

Colors Employed: Thayer Blue and White

Type Plans

Typical deception patterns of the Thayer System are shown on PLATES IV to XII inclusive. Patterns are shown for both port and starboard sides, and should be so used in order to get the best end-on effects. Though shown for certain specific classes of ships, the designs can and should be adapted to other types and classes

Basically, Liberty Ships were painted in Measure 14, overall 5-O Ocean Gray...in FS #, that equates to 35164.
Some ships under navy control were painted in Ms 21 and 3x camo schemes, but the vast majority, including the O'Brien, were Ms 14. Here's the official instructions:
Vertical Surfaces:
Vertical surfaces from boot-topping to top of superstructure masses, Ocean Gray 5-O.
Pole masts, yards, slender upper works above level of top superstructure masses, Haze Gray, 5-H.
Horizontal Surfaces:
Horizontal surfaces, Deck Blue, 20-B.
Wood Decks.
Wood decks except on submarines and carriers shall be darkened to the color Deck Blue. Deck Blue paint shall be used in lieu of stain for this purpose.
Canvas Covers.
Canvas covers visible from the outside vessel are to be dyed a color corresponding to Deck Blue.
Notes:
The camouflage painting need not be exact or carried into corners. Small gear, wires, rigging, and areas permanently in shadow, as under boats, etc., need not be painted with the camouflage colors. There is no objection to exact or careful painting which may be desired for the sake of good appearance at close range.
All bright or shiny objects, no matter how insignificant, shall be painted, covered, or removed

<klik to enlargeOf course all the camo in the world didn't help the Jeremiah O'Brien recently... ATTN modders: The recent photo in the SF Chronicle is a a 'no bullshot of an actual burning Liberty ship. if ever! I cannot believe some adept modder can't adapt this to SH-V at least; to effect 'total immersion' realistic graphics of a burning WWII cargo ship!!?? Then of course there's the USS Allegan AK-225 in a less than dazzling camo worth noting!!?? Her camouflage is Measure 32 Design 1F.

[U-190]

Absolutely brilliant!

[Aktungbby]

Not really; but thanks! the subject came up in Atoka220's thread: https://www.subsim.com/radioroom/sho...44&postcount=1 And I responded accordingly as I'm often aboard the USS Jeremiah O'Brian parked next to the Gato class USS Pampanito in SF's Fisherman's Wharf. The photos of the warehouse fire that scorched the Normandy survivor are terribly authentic; no imho 'bout it. Seeing such in real time should be a modders dream as to authenticity!! https://www.subsim.com/radioroom/sho...78&postcount=8

[Mister_M]

Originally Posted by Aktungbby

"(B) In Atlantic or Pacific Coastal waters where weather is generally sunny, visibility is high, and bright moonlight is common at night.
Measure 14-Ocean Gray System"

That's very strange because with this light grey painted on the hull, ships will be very well noticeable at night when there is moonlight... At least, it's my opinion... Perhaps moonlight is not enough to spot light grey ships' hull from far distances... but this would be surprising to me.

Else, interesting discussion here : http://cs.finescale.com/fsm/modeling...7/t/33023.aspx

[gap]

Recently I have been digging on the internet for information on the ensigns worn by various types of British and Commonwealth vessels, and I thought I would share my findings here in case someone is interested.

• Commonwealth merchant vessels
  Looking into Lloyd's records of merchant ships owned by Commonwealth steamship companies, I was surprised to discover that all of them were registered as British-flagged ones, no matter if their companies were actually based in the UK or not.
  
  The 2,053-ton bulk carrier Magog, for example, was owned by Canada Steamship Lines, a Montreal-based shipping company. As expected, uboat.net reports the ship as Canadian but convoyweb.org and, more importantly, the 1939 Lloyd Register have her as British. I have checked many other Canadian, Australian, New Zealand, etc. vessels, and they all were registered as British. As far as I can see there are two possible explaination to that:
  
  
  1. all the merchant vessels of the Commonwealth wore the Red Ensign;
     
     
  2. vessels belonging to (former) British colonies wore the Red Ensign (optionally) defaced with each country's national emblem, but Red Ensign variants were still officially considered (and registered) as British flags.
  
  In order to investigate the veracity of the last point I have checked many photographs. Discernig small flag details based on pictures which usually have a poor resolution is not so easy, nonetheless I think I have found a few photographs which seem to confirm my hypothesis.
  
  
   

  
  The picture above and the one below portray the Morialta and the Ulooloo respectively, both owned by Adelaide Steamship Company
  
  
   

  
  Both vessels have a Red Ensign hoisted on the flagstaff. The Union Jack on flag's canton is easily discernible, but can you see the white spot beneath it? Well, I am not 100% sure, but that might be one of the stars defacing the Australian Red Ensign
  
  One last picture, this time of the Princess Marguerite, a passenger ferry managed by British Columbia Coast Steamships, a division of the Montreal-based Canadian Pacific Railway Company
  
  
   

  
  Again, a brighter spot is barely discernible; that migh be the bottom portion of the coat of arms defacing the Canadian Red Ensign
  
  
• Catapult Aircraft Merchant ships/Merchant Aircraft Carriers
  Those were merchant vessels, owned by the Ministry of War Transport but managed by private companies and commanded/crewed by civils, threfore the regular civil (red) ensign was flown aboard them.
  
  
• Armed Merchant Cruisers
  They were merchant ships requisitioned by the Admiralty and commissioned in the Royal Navy for convoy defense. They were given the HMS prefix and, as any other naval vessel, they wore the White Ensign.
  
  
• Royal Fleet Auxiliary ships
  Mostly oilers, depot ships, fleet tenders, etc, either purpose-built or requisitioned for that purpose. They were commanded and crewed by members of the Royal Naval Reserve, they were given the RFA prefix and they wore the Admiralty Blue Ensign (former Transport Ensign): a Blue Ensign defaced with a horizontal yellow anchor.
  
  Source: http://www.historicalrfa.org/archive...ign-of-the-rfa
  
  
• Q-ships
  Basically heavily armed AMCs in disguise.
  
  

  In 1939 Winston Churchill gave authority for a number of merchantmen to be requisitioned for service as Q-ships, although for security purposes they were referred to as Special service Freighters. A fleet of nine small mainly coal-burning vessels were acquired , six for deep-sea work and three for coastal work. All were commissioned as HM ships under their original names but were given RFA cover names and on entering harbour and while in harbour they wore the Blue Ensign, behaved as RFA’s and adopted the RFA commercial practices. None of them was really suitable for their intended roles and met with a complete lack of success. Their Q-ship service officially ended on 2 March 1941

  Source: http://www.historicalrfa.org/rfa-cha...ip-information
  
  
• Royal Mail Ships
  A number o merchant vessels, especially ferries and ocean liners, were given the RMS prefix and designated to carry mail under contract to the British Royal Mail.
  The Flags of the Word project lists a Royal Mail Blue Ensign and the National Maritime Museum of Greenwich has one of these ensigns in its collection. Apparently this flag was worn by RM ships after 1902, but I ignore wether it was still in use at the oneset of WWII, when most RM ships were requisitioned as troop transports and swithched to other flags.
  
  
• Hospital Ships
  During WWII the Ministry of War requsitioned a number of private-owned ocean liners for use as hospital ships. The appearance of those vessels was regulated by the Hague Convention of 1907 and subsequent international agreements.
  
  

  It had long been acknowledged that the system of marking hospital ships adopted in 1907, at a time when air forces did not exist, was completely inadequate. Hospital ships were to be painted white outside with a horizontal band of green or red, and were to fly the red cross flag. The experts who met in 1937 recommended that large red crosses on a white ground should be painted on the hull and deck of hospital ships. During the Second World War, the belligerents often adopted that means of identification. It is clear from the records that the lack of an up-to-date system of marking, visible at a great distance, was the cause of most of the attacks made on hospital ships during the Second World War.
  
  [...]
  
  The national flag of the belligerent must be flown. On the other hand, a hospital ship will not fly the pennant hoisted by warships.
  Hospital ships belonging to a neutral State and assisting a belligerent must fly their national flag as well as that of the belligerent concerned. The records of the 1907 Conference at The Hague indicate where the flags should be flown: the flag of the neutral State is to be flown in its usual place, and the flag of the belligerent together with the red cross flag is to be flown from the mainmast.
  Last and most important, hospital ships must fly a white flag with a red cross. That provision already existed in the earlier instruments, but the 1949 Diplomatic Conference decided to specify where it should be flown, although that place had already become traditional as may be seen from the reference above: it is to be flown at the mainmast, as high as possible. Why should this be so? Because it is the part of the ship which first appears over the horizon. The white flag with a red cross will therefore be placed above the flag of the belligerent.

  source: https://ihl-databases.icrc.org/ihl/0...2563cd00424636
  
  Summing up, the general rule for hospital ships was to fly their national ensign "in its usual place" (i.e. at ship's stern while underway) + red cross flag on the mainmast "as high as possible" + the national ensign of the concerned belligerent if the ship belonged to a neutral country.
  
  Now the matter is: which was the ensign used aboard Commonwealth hospital ships? The following document (p. 7, fig. 9), gives a contradictory answer:
  
  https://maritimearchaeologytrust.org...-Burns_WEB.pdf
  
  The flag shown in fig. 9, p. 7 is a Board of Trade Blue Ensign, yet the caption reads: HMHS Lady Connaught Flag: “A Blue Ensign Flat”.
  
  A thread on Great War Forum sheds some light on the issue:
  
  

  A recent thread about the correct prefix for hospital ships ventured into some interesting byways which included debate about the ensign flown by hospital ships. It was pointed out that hospital ships were not commissioned into the Royal Navy and therefore would not have flown the white ensign, and that all warrants to fly the plain blue ensign were cancelled in August 1914, so the choice was between the red ensign and a blue ensign defaced with a horizontal anchor, sometimes known as the Admiralty Ensign. For anyone interested in this debate, I have just come across a 1917 HMSO pamphlet entitled 'Correspondence with the German Government regarding the Alleged Misuse of British Hospital Ships' which, as well as being an interesting read, seems to resolve the ensign question.
  
  The pamphlet contains memoranda from the German Government (delivered via United States embassies) documenting the allegations of misuse and advising Britain that it intends as a consequence to treat as belligerent any hospital ship encountered in the southern North Sea, the English Channel and parts of the Mediterranean. The pamphlet also contains the British Government's detailed rebuttals to each of the allegations. One of these contains the sentence (p 12), 'All British hospital ships have their names painted distinctly on them in the usual place, and all fly the Red Cross flag and the British defaced Blue Ensign worn by transports.'

  The text above is relative to WWI, nonetheless a similar restriction to the one of 1914 was issued in 1939 ("All Blue Ensign warrants were cancelled in 1939"), so it is unlikely for Britsh hospital ships of WWII to have flown the "Blue Ensign flat". Instead of that, the probably following the WWI usage of the Transport Ensign, or they might have switched to the Board of Trade Ensign.
  
  
  Infantry landing ships
  According to Wikipedia (mentioning as reference: Bruce, Colin J. Invaders, Chatham Publishing, London, 1999 ):
  
  

  Some of the LSIs were commissioned into the Royal Navy, received navy crews, and flew the White Ensign, while most retained their civilian crews and flew the Red Ensign.

• Troop transports
  Here I wish we had more information. The one source I have found so far is a comprehensive study on British ensigns published in 2015
  
  Among the other flags, it mentions (at p. 29):
  
  

  Department for Business, Enterprise and Regulatory Reform Circular Picture of Three Masted Ship at Sea. Available for use on land, and on any vessels that the department might operate. It was originally the Board of Trade ensign, and has had a variety of uses. In the 1920s troopships carrying army or air force personnel flew it and in the 1960s UK Trade Commissions used it as a car flag.

  Whether the usage of the Board of Trade Blue Ensign started in the 20's lasted until WWII or not is a mystery to me, but it is likely that, similar to infantry landing ships, some troopers manned by civilian crews might have flown the Red Ensign.
  

Summary of the flags mentioned in this post and their usage:

Merchant vessels / Some troop transports (?) / Some Landing Ships / CAM/MAC ships
British Red Ensign *

As above
Australian Red Ensign

As above
Canadian Red Ensign

As above
New Zealand Red Ensign

As above
South African Red Ensign **

Royal Mail Ships (?)
Royal Mail Ensign

Royal Fleet Auxiliary vessels / Q-ships / Hospital Ships (?)
Admiralty, Government
Service or Transport Ensign

Troop Transports (?) / Hospital Ships (?)
Board of Trade Ensign

Vessels commissioned in one of the Commonwealth navies (ilcuding some landing ships), except Q-ships
White Ensign

_______________________

Notes

* The Red Ensign (undefaced) was also the civil ensign flown aboard merchant vessels registered in British India. While the Raj had its own version of the Red Ensign defaced with the so called "star of India", this flag had only a limited use:

No Admiralty Warrant was issued for this ensign which was an unofficial, or semi-official land flag. It was used between 1945 and 1947 in the context of India's membership of the United Nations, and possibly used earlier to denote India's membership of the League of Nations.

Source: Flags of the World

[...] the Red Ensign was used as the civil ensign and sometimes represented India in international events, notably in the Declaration by United Nations during World War II. The ensign used on merchant ships registered in British Indian ports was the undefaced red ensign.

Source: Wikipedia (see link above)

** Since 1928 South Africa had its own national flag, nonetheless...

The South African "Red Ensign" used unofficially as a de facto national flag until 1928 [...] continued being used sparsely in limited contexts until the early 1950s.

source: Wikipedia (see link above)

Even after the Union adopted the new national flag in 1928, it continued to use the South African Red Ensign in its proper role as the Merchant Marine ensign until 1951 before the Merchant Shipping Act of that year designated the orange-white-blue national flag also as the Merchant ensign.

The Red Ensign was for use at sea as the merchant fleet ensign. This version of the South African Red Ensign continued in use in the merchant navy until 1951 when it was finally displaced at sea by the South African national flag in terms of the Merchant Shipping Act of that year.

Various sources inform us that the Red Ensign with South African flag badge was replaced by the South African national flag as the merchant ensign in 1951, and some writers state that this was in terms of the Merchant Shipping Act 1951. Well, section 65 of this Act, in its original form, did indeed state that "the national flag of the Union is hereby declared to be the national colours for all ships registered in the Union" -- but the Act wasn't brought into operation in 1951. It was kept in abeyance for several years.

Source: Flags of the World

_______________________

That should be all for now guys. In case you find any wrong information, if you think I have missed some notable flag or vessel type, or if you can provide new information relevant to the subject of this post, I will gladly update it with your imputs

[U-190]

Originally Posted by gap

Recently I have been digging on the internet for information on the ensigns worn by various types of British and Commonwealth vessels, and I thought I would share my findings here in case someone is interested.

• Commonwealth merchant vessels
  Looking into Lloyd's records of merchant ships owned by Commonwealth steamship companies, I was surprised to discover that all of them were registered as British-flagged ones, no matter if their companies were actually based in the UK or not.
  
  The 2,053-ton bulk carrier Magog, for example, was owned by Canada Steamship Lines, a Montreal-based shipping company. As expected, uboat.net reports the ship as Canadian but convoyweb.org and, more importantly, the 1939 Lloyd Register have her as British. I have checked many other Canadian, Australian, New Zealand, etc. vessels, and they all were registered as British. As far as I can see there are two possible explaination to that:
  
  
  1. all the merchant vessels of the Commonwealth wore the Red Ensign;
     
     
  2. vessels belonging to (former) British colonies wore the Red Ensign (optionally) defaced with each country's national emblem, but Red Ensign variants were still officially considered (and registered) as British flags.
  
  In order to investigate the veracity of the last point I have checked many photographs. Discernig small flag details based on pictures which usually have a poor resolution is not so easy, nonetheless I think I have found a few photographs which seem to confirm my hypothesis.
  
  
   

  
  The picture above and the one below portray the Morialta and the Ulooloo respectively, both owned by Adelaide Steamship Company
  
  
   

  
  Both vessels have a Red Ensign hoisted on the flagstaff. The Union Jack on flag's canton is easily discernible, but can you see the white spot beneath it? Well, I am not 100% sure, but that might be one of the stars defacing the Australian Red Ensign
  
  One last picture, this time of the Princess Marguerite, a passenger ferry managed by British Columbia Coast Steamships, a division of the Montreal-based Canadian Pacific Railway Company
  
  
   

  
  Again, a brighter spot is barely discernible; that migh be the bottom portion of the coat of arms defacing the Canadian Red Ensign
  
  
• Catapult Aircraft Merchant ships/Merchant Aircraft Carriers
  Those were merchant vessels, owned by the Ministry of War Transport but managed by private companies and commanded/crewed by civils, threfore the regular civil (red) ensign was flown aboard them.
  
  
• Armed Merchant Cruisers
  They were merchant ships requisitioned by the Admiralty and commissioned in the Royal Navy for convoy defense. They were given the HMS prefix and, as any other naval vessel, they wore the White Ensign.
  
  
• Royal Fleet Auxiliary ships
  Mostly oilers, depot ships, fleet tenders, etc, either purpose-built or requisitioned for that purpose. They were commanded and crewed by members of the Royal Naval Reserve, they were given the RFA prefix and they wore the Admiralty Blue Ensign (former Transport Ensign): a Blue Ensign defaced with a horizontal yellow anchor.
  
  Source: http://www.historicalrfa.org/archive...ign-of-the-rfa
  
  
• Q-ships
  Basically heavily armed AMCs in disguise.
  
  
  
  Source: http://www.historicalrfa.org/rfa-cha...ip-information
  
  
• Royal Mail Ships
  A number o merchant vessels, especially ferries and ocean liners, were given the RMS prefix and designated to carry mail under contract to the British Royal Mail.
  The Flags of the Word project lists a Royal Mail Blue Ensign and the National Maritime Museum of Greenwich has one of these ensigns in its collection. Apparently this flag was worn by RM ships after 1902, but I ignore wether it was still in use at the oneset of WWII, when most RM ships were requisitioned as troop transports and swithched to other flags.
  
  
• Hospital Ships
  During WWII the Ministry of War requsitioned a number of private-owned ocean liners for use as hospital ships. The appearance of those vessels was regulated by the Hague Convention of 1907 and subsequent international agreements.
  
  
  
  source: https://ihl-databases.icrc.org/ihl/0...2563cd00424636
  
  Summing up, the general rule for hospital ships was to fly their national ensign "in its usual place" (i.e. at ship's stern while underway) + red cross flag on the mainmast "as high as possible" + the national ensign of the concerned belligerent if the ship belonged to a neutral country.
  
  Now the matter is: which was the ensign used aboard Commonwealth hospital ships? The following document (p. 7, fig. 9), gives a contradictory answer:
  
  https://maritimearchaeologytrust.org...-Burns_WEB.pdf
  
  The flag shown in fig. 9, p. 7 is a Board of Trade Blue Ensign, yet the caption reads: HMHS Lady Connaught Flag: “A Blue Ensign Flat”.
  
  A thread on Great War Forum sheds some light on the issue:
  
  
  
  The text above is relative to WWI, nonetheless a similar restriction to the one of 1914 was issued in 1939 ("All Blue Ensign warrants were cancelled in 1939"), so it is unlikely for Britsh hospital ships of WWII to have flown the "Blue Ensign flat". Instead of that, the probably following the WWI usage of the Transport Ensign, or they might have switched to the Board of Trade Ensign.
  
  
  Infantry landing ships
  According to Wikipedia (mentioning as reference: Bruce, Colin J. Invaders, Chatham Publishing, London, 1999 ):
  
  
  
  
• Troop transports
  Here I wish we had more information. The one source I have found so far is a comprehensive study on British ensigns published in 2015
  
  Among the other flags, it mentions (at p. 29):
  
  
  
  Whether the usage of the Board of Trade Blue Ensign started in the 20's lasted until WWII or not is a mystery to me, but it is likely that, similar to infantry landing ships, some troopers manned by civilian crews might have flown the Red Ensign.
  

Summary of the flags mentioned in this post and their usage:

Merchant vessels / Some troop transports (?) / Some Landing Ships / CAM/MAC ships
British Red Ensign *

As above
Australian Red Ensign

As above
Canadian Red Ensign

As above
New Zealand Red Ensign

As above
South African Red Ensign **

Royal Mail Ships (?)
Royal Mail Ensign

Royal Fleet Auxiliary vessels / Q-ships / Hospital Ships (?)
Admiralty, Government
Service or Transport Ensign

Troop Transports (?) / Hospital Ships (?)
Board of Trade Ensign

Vessels commissioned in one of the Commonwealth navies (ilcuding some landing ships), except Q-ships
White Ensign

_______________________

Notes

* The Red Ensign (undefaced) was also the civil ensign flown aboard merchant vessels registered in British India. While the Raj had its own version of the Red Ensign defaced with the so called "star of India", this flag had only a limited use:



Source: Flags of the World



Source: Wikipedia (see link above)

** Since 1928 South Africa had its own national flag, nonetheless...



source: Wikipedia (see link above)







Source: Flags of the World

_______________________

That should be all for now guys. In case you find any wrong information, if you think I have missed some notable flag or vessel type, or if you can provide new information relevant to the subject of this post, I will gladly update it with your imputs

Thanks for your hard work, gap!
By the way, American pilots who joined the British Air Force also fought under the British flag in the Battle of the English Channel. They were seconded to the British forces. This applied not only to airplanes but also to ships.

[gap]

Originally Posted by Aktungbby

https://maritime.org/doc/camo/index.htm

Oh, wow, thank you mate, that document is a gold mine but...

The publication shall be destroyed by burning when no longer required. No report of destruction need be submitted.

Should I burn my computer after reading?

Before I do it, I have created a table which should cover most of the paint colours mentioned in the document (HEX values taken from here):



Talking about the so called "Measure 16-Thayer System", I read that it was specifically designed for weather conditions similar to North Atlantic ones but, as far as I can understand, only troop transports and cargo ships commissioned in the US Navy were painted with it. The following link has a comprehensive list of vessels to which the said pattern might have applied:

https://www.ibiblio.org/hyperwar/USN/USN-ships.html

What I wonder is: which was the exact employment of those vessels by USN? Would they sail within mixed convoys?

http://www.convoyweb.org.uk/ might have some answers

Originally Posted by Mister_M

That's very strange because with this light grey painted on the hull, ships will be very well noticeable at night when there is moonlight... At least, it's my opinion... Perhaps moonlight is not enough to spot light grey ships' hull from far distances... but this would be surprising to me.

Else, interesting discussion here : http://cs.finescale.com/fsm/modeling...7/t/33023.aspx

Another interesting link. Thank you for sharing

Originally Posted by U-190

Thanks for your hard work, gap!

Thank you mate, my own pleasure

Originally Posted by U-190

By the way, American pilots who joined the British Air Force also fought under the British flag in the Battle of the English Channel. They were seconded to the British forces. This applied not only to airplanes but also to ships.

I had already read that during Normandy landings (or maybe it was for Operation Torch, I don't remeber now), US aircraft had adopted British markings, I wasn't aware of the British ensign being flown on US ships though. Do you have any link which might add some detail?