What color should I paint my new darkroom?

If you like black walls and don't like dust accumulation on fabric, you can do what Ctein does in his darkroom. He didn't bother to paint or even build walls, he just hangs heavy black construction plastic. Claims it is the best way as it attracts dust that can be easily washed off. Probably true but I wouldn't want to work in there.

That wouldn't work well for doing infrared film, the plastic transmits the IR way too easily.