Robair Robair:
Ego over practicality/safety I guess.
Radar/IR missiles doesn't care if the jet is gun-metal Grey or florescent pink. If it is being shot at by machine gun or cannon fire, whether from a combat jet or from a shooter on the ground, I doubt it really makes much of a difference what the colour is.
Think about it this way, when we as a country were ready to go to war with the Soviets, this was the basic colour scheme for all non-combat aircraft. This whole gun-metal grey theme didn't really come about till the end of the cold war. If the colour was such a critical factor for non-combat jets, the airforce would have been running the gun-metal grey colour scheme for all aircraft since 1946.