For the WWII era stuff Brodak Piper Blue is a really good blue right out of the can. Their Polar Grey is also a really good grey right out of the can. Use Madrid Red, Insignia White, and Insignia Blue on the fin/rudder for the early WWII planes. That's everything I used on the PBY, all right from the can.
On the Helldiver I used Piper Blue on the top, a mixture of Piper Blue with Polar Grey added for the middle, and their Insignia White on the bottom. I used Polar Grey for the canopy work.
On Keith's P-47 we used Brodak Olive Drab and Polar Grey for the camo on top and then Platinum Grey on the bottom. We used Platinum Grey on the bottom so there would be a noticable contrast to the Polar Grey used on the top. There is a big difference between the two colors. The Invasion stripes are Insignia White and Jet Black. All of these colors were used straight from the can as well.
On my Shark 402 I painted the entire plane Polar Grey first and then put Insignia Yellow over that on the wings. The nose and wing stripes are Miami Blue. I used Polar Grey mixed with Jet Black to get a dark grey for the canopy. I keep a jar of that mixture on hand for canopies on light colored planes. The fin/rudder on the Shark 402 uses the same colors as the PBY.
For the Navy Training scheme on the recent Challenger .15 I used Brodak Insignia White, Jet Black, and Cruiser Orange, again all straight from the can.
Keep an inventory of these few Brodak colors on hand and you can pull off a
lot of believable Military schemes quite easily.