I Guess Sometimes Black Is The New Green

Thanks to another co-worker of mine, I learned today about this environmentally-friendly alternative to the main Google site. As far as I can tell, it's still Google; it just uses less energy in its display (or so the claim goes), thanks to having a black background. I certainly like the thinking behind it, although I don't understand the impact of white vs black screens well enough to say if it's actually effective. Thoughts?