Ah ok, stupidity on my part in both cases! It actually does work, but after skimming the description I assumed it was for styling 'View Source' tabs. Which would be a great feature btw.
What I do to save my coder sanity is not try to write serious code in my web browser.
I've recently switched to [Solarized](http://ethanschoonover.com/solarized), which offers both options, but I think it excels at keeping contrast comfortably low.
Perhaps you should showcase some of those themes in the screenshots... I, too, dismissed your extension out-of-hand, and only noticed the theme selection dropdown after reading your comment.