underside of wings and fuselage should be same color. Upper surfaces and fuselage deck OD. By the end of the war these aircraft were being delivered in complete OD.
What unit and aircraft are you looking to do?
Many of these USAS units were late in painting full markings on their machines. A number of photos showing full markings tend to be taken at the end of the war or after.
Here is a profile of the DH from 20th Aero from my website. I did a 1/72 scale model of this exact plane and used my 20th logo I did for the profile to make decals. The kit was a Pegasus kit. Not a bad kit.