No -Gs were night fighters, from memory. That's clearly an OD paint scheme (look at the wingtip). Like I've said before, color film back then was primitive. Much more so than what we have today. The processing and the development of film and photos, coupled with the film that couldn't differentiate between all colors, often meant that colors showed up wrong.
Looks like the image was either:
1) over exposed when taken, they didn't have sophisticated light meters like we do now
2) not stopped 100% when printed, so that it got darker over time, or burned when printing
3) Just couldn't get the color on the film properly, and/or scanned improperly to get it into digital format.
My $0.02