The YS2 was green, the same as most other bombs. The WE177B was white probably for better thermal protection once released. The WE177C was probably green for camouflage whilst being carried.
However you might have a point CM.
At one presentation a gentleman, who wore crimson pants or some such, when told that the bomb would impact and the laydown timer start asked:
"What would happen if I sent a man with a satchel charge and blew it up?"
When told there probably wouldn't be time said:
"Well what would happen if I shot it with my gun?"
So there you have it. Britain's nuclear deterrent neutralised by Herr Grubber and his little tank.