Paint schemes don't seem to be closely coupled with specifications of aircraft in Aces High otherwise there'd be only one paint scheme available for the Brewster.
From an old article of the day a P51B(I think) increased its top speed by 8 MPH without paint. The New York times also did an article about deleting the paint and its benefits. That would make the P38L's top speed faster than the J by about the same amount..
Two hundred kits were being flown so they could not have weighed a great deal. My guess is the P38L may have weighed 100-200 pounds less than the painted J.
Best I can tell too the default skin is the one used for reflection properties so camouflaged P38Ls still shine. We need something to counteract that shiny, big target in the sky.
