The Basic dark/light/pastel paints don't have any gain or loss. Only ones in the Paint category to have environmental loss are 2 from CL (Faded Memories and "Mold"ed Baseboard) and of course the Drywall. Most others have gain or gives industrial. Doesn't matter what colour you pick.
To be honest, my sim didn't even mind the plain Drywall. I had him stay in a room for a few hours, and he didn't care. Don't know if traits have anything to do with it. I'd be surprised if it does, though. It bothered ME more than him, if I'm honest, I don't like plainly painted walls, especially white. I find it boring.