I figured it out with this:
.sidebar-primary { background: #ffe6d1; }
Things are looking much better (check the link again), but I am having trouble changing the color of the bbPress sidebar. I’m using the bbPress specific sidebar from ‘bbPress WP tweaks’ and it doesn’t seem very customizable.
CSS is still a bit mysterious to me, but it seems that I should be able to have a snippet that changes the background color for this particular widget.
Thank you both! The CSS did the trick and yes, I would like to be a bit more stylish.