With the launch of themes for Gmail, Google now allows you to choose your own Gmail colors. Just click on the Settings link in the upper right hand corner of your screen, select the Themes tab, and find the "Choose your own colors" option at the bottom of that page. You'll be able to select colors for everything from the background of your inbox to link text.
The color picker also allows people with visual disabilities to tweak Gmail into something more comfortable for them, whether it's increasing the contrast between colors or ridding their inbox of bright white. The "Reset" button will let you revert to the defaults. Note: Companies that use Google Apps won't see the options for themes yet.