There's some research published at the IPMS Canada webpage on this very question.
Christian, the red is optional on the Pilot's personal effects, not on the aircraft.
When once you have tasted flight you will walk the Earth with your eyes turned skyward.
For there you have been, and there you will always long to return.
-Leonardo Da Vinci
Best I can offer is out of eaglefiles #4 "tigers over china". There wasnt a dupont match for the prescribed RAF color "sky type S". So they propose that FS 16473 aircraft gray is the likely candidate. A cool light gray with a very slight blue green tinge.
"...Fat, drunk, and stupid is no way to go through life son"