I agree with Blakwhit, the green was camouflage for downed fliers. The USN used to have orange flight suits to aid rescue at sea, and so did USAF Air Defense Command interceptor pilots, on the principle that if they went down it would be on friendly territory and they would be better visible to rescuers. Vietnam pretty much ended all that and everybody went to green, also roughly coinciding with the adoption of Nomex.
I have read that in the '60s the Thunderbirds had red, white, blue or gray "show suits" they would rotate. The white was not popular, especially with the slot pilot, because it showed every particle of soot from the engine exhaust.
Another thing that happened in Vietnam was the world of USAF "party suits," which were privately made for off-duty wear and came in a rainbow of squadron colors.
I don't know anything about RAF blue suits, but some googling came across a few like this:http://www.historicflyingclothing.com/e ... 5Y8aTXLJIF