In Themes: How to colorize the entire page

First off we'd like to thank Zoho team for the new mail appearance. The old one was just, uhmm, old.

Now about the new look, the current themes allow only changing the side bar colors so I was wondering if there's a way to change the content areas as well?

I wish for dark reading area because staring at white screen for hours everyday just gets tiring to the eyes.

Thanks and conragtulations.
Sbook