Are you a frequent Googler? Concerned about energy usage? Well, set your home page to http://www.blackle.com. It's the same old Google, only the background is black. It takes more power to display a white page than a black one.
Smarty-pants Doogie Houser used a blue background in Word when writing his electronic diaries. It was quite irritating to look at. I wonder if he did it to earn carbon credits.