Changing background colour, and sidebar background colour?

Hi, I’m using the default WP theme, because I like it. But I’m kind of tired of the white background. Can I change it to a different colour? I’d also like to change the background of the sidebar, if that’s possible.

I tried doing it once via style.css, but had no luck.

If someone can explain to me how to do it, it would be much appreciated ??