Are you going to use the airplane for combat? If so, cover it with dove gray iron on film like monocote or ultracote. Scuff the film lightly with 00 steel wool and then clean it with alcohol to get the residue off. Paint the upper surfaces with hunter green or dark hunter green Rustoleum--it's as close to IJN dark green as anything else you'll find. It's cheap and fuelproof up to about 15% nitro after it cures, which takes 3-4 days. No clearcoat needed. Stick the decals on and you'll be flying while everyone else is busy mixing paint trying to get the exact color, which will be real hard because no one really knows what the "real" color looked like!