You selected a grand old airplane with the Skyraider. I flew them from Nakhon Phanom, Thailand back in 1969 and 1970 and that "Midnight Cowboy" airplane, #257, was "my" airplane during that time!
It was white underneath at the onset. It was also called "Sopwith Camel" until that motion picture came out. I was being assigned so many midnight missions and I liked the movie's music so much that it seemed like "Midnight Cowboy" was the obvious choice for the cowl name.
The airplane was eventually painted black on the undersides so a model could be either white or black underneath and be accurate.
I have photos of both and if you'd want them, send me an e-mail address and I'll send them on line.
"Of course", I have THREE of the large Trumpeter Skyraider kits and will start the first one shortly.
Spad