I think it'd be cool if there was an option in the user control panel to change the color theme of the site (i.e. change the grayish-blue colors into red, etc).

I believe a new theme is in the works so this could be counterproductive, however, if one is in the works this would be a neat feature to keep in mind while developing it. Don't take this statement as factual.

Fun idea but requires more work than you'd think, especially if it were to be specific to each person's options. It'll be something to consider for the main site maybe (when I finally get around to updating its looks) but not something I can easily integrate into the forums.