I think a soft color would look great.
I went onto the Sherwin Williams site, sherwin.com, and think either of these two colors would go great for the walls: Agreeable Gray 7029 or something like Icy 6534 (which is like a light periwinkle blue). If you go to the site, there's a "color visualizer" you can check out.
Lighter colors make rooms appear larger and they let a lot more light in as well. Darker colors have the opposite effect. Not to mention I'd be afraid a dark color would feel depressing and maybe even inspire scary dreams
Lighter colors are relaxing and are especially good for bedrooms because give you this clear mind kinda feeling