Customizing look and feel

I know I’ve found the answer to this in the past, but I can’t seem to find
it anywhere now.

How do I change the background color of RT?

I’ve replaced the gradient file, and that works for the top portion of the
RT main page…but I can’t seem to change the bottom portion of the RT
main page no matter what I try modifying in the .CSS files.

Thanks,

-jake