I have forgotten where I got this from but a few years ago, I read somewhere that LCD and CRT screens (That means your monitor) use less energy or electricity when the images shown are in dark colors.
That is also one of the reasons why my blog design is in dark colors.
Therefore Google, one of the highly successful search engines on earth have created BLACKLE.COM
A search engine where as opposed to google, has black for background, cutting a bit on your electric bill. It also help reduce green house gas emissions. Collectively when a number of people(let's say half the planet) use it then it will have great effects and our efforts won't have been in vain.
I use it as my homepage. The url is www.blackle.com
Do your share for mother earth.