A number of people, including those that run the sites Blackle and Darkoogle, have argued in the recent past that Google should turn its homepage (and results background) from white to black to save energy. (Both of the above sites use the Google custom search engine). Here’s some background on the controversy from US News. Google counters that black screens actually use more energy than white and they point to research that appears to confirm this. On a larger front, Google is part of the Climate Savers Computing initiative that seeks to make computer hardware and data centers more energy efficient.
So while green is certainly the new black, black may not be the new green after all.