My understanding is that pre war bikes were RAF blue/grey(gloss)and wartime production was drab green/brown of the appropriate shade for the year of manufacture...
Blue bikes were repainted into the later drab colours at overhaul or before if deemed necessary...Ian
I'm not an expert on the exact dates colours were introduced/superceded...
Early war machines were 'Khaki Gas Proof No.3'..a browny green colour.
Mid war machines were 'Dark Camouflage Brown'...I'm not sure how much this was used though, there seem to be few original machines bearing the remains of that colour..
Late war machines were painted 'British Dark Olive Drab'....
The last two colours are available from military paint suppliers...I'm unsure about the KGP No3...I did hear it is now being produced....
Sorry to be a bit vague but I use KGP N03 which I mix myself, so I don't have any paint codes etc... Ian