Here is my analysis of the commodore's (Hugh Hext Rogers) drawing of convoy OB.330 ships (
assuming that colors are accurate) :
1.
Ships with their original colors : hulls are black (sometimes dark grey), and upper structures are white, light yellow, buff or brown, funnels have different colors (orange, blue, black). MANAQUI is plain dark grey (maybe a repaint ?). Many of them are British (so "rules" are not very respected...).
2.
Ships with hull (probably) repainted in grey : most of ships are tankers, it's a light grey paint.
3.
Ships with superstructures (probably) repainted in grey : the hull remains very dark (black). HEINA superstructures are perhaps actually white...
4.
Ships in plain grey (probably a war repaint) : note that there are different shades of grey from ship to ship...