When it was decided that our VC10Ks should be repainted in 'John Major Grey' rather than hemp, ZA149, the first one to be repainted, looked awful with a wedgewood blue cheat line, including along the engine nacelles. The 'blue vein' as it became known.... The aircraft also had white lettering and 'they' were told to try again! So the blue vein and white lettering were changed to dark grey, which looked far better!
Presumably the grey paint was the result of there being far fewer of Pusser's war canoes to paint, so the MoD had sheds full of grey paint going cheap?