Yes it does go on. I have just re visited the Vanpelt site (American)again.
It states, about colours, that Ford and Merc engines, through 1940 to 1942 were dark green. Then it said Merc engines were dark blue from 1941 to 1948.(one contradicts the other) Post war Fords were blue, and that truck engine paint colours generally were the same as car engines. I imagine in the U.K. that at times there were issues with supply of paint pigments, along with every thing else, and that the power unit colours were not always one colour.
I guess if one is really embarassed about the colour, then they could always leave the engine covers on
Ps. From a mechanics point of veiw,black is the worst possible colour because you cannot see anything. Its just a black hole, and you cant see any faults. Yellow is great! but for a carrier Blue or Green is bang on!