The 1/48 Revell B-17G contains 2 decal options, one for El Lobo II which is the natural metal finish bird on the box, and also decals for Chow Hound which is an olive drab over neutral gray bird.
When the war broke out, The B-17 had a natural metal finish, but the finish was changed shortly thereafter to olive drab over neutral gray camo until late in the war when the natural metal finish came back.
When painting, though you might want to lighten your olive drab a little bit, with any of these colors- gray, white, tan, yellow. This lightens the shade of OD a little bit and makes it more realistic as a factory fresh OD finish on a real world plane would not last long.
-Matt
On The Bench: 1/48 HK B-17G "Man-O-War II"
On Deck: 1/48 Tamiya P-38H, 1/48 Revell PV-1