A few months ago, TreeHugger Mark Ontkush wrote a post on his blog EcoIron entitled "Black Google Would Save 750 Megawatt-hours a Year." The post lays out the following train of thought: “An all white Web page uses about 74 watts to display, while an all black page uses only 59 watts.” Google, which has a white background and gets about “200 million queries a day” could reduce global energy use by 750 Megawatt-hours a year by simply changing the color of its homepage to black.
In response to this post, a black version of Google emerged called Blackle.com. According to Blackle’s homepage at publication time, 137,774.672 Watt hours have been saved. The site encourages users to “make a difference today" by 'Blackling' or visiting TreenHugger.com, a blog dedicated to environmental awareness.
It looks like Google has its own version now too at: