But I didn't think of this:
Treehugger.com | Black Google Would Save 750 Megawatt-Hours a YearOkay, $75,000 a year divided by however many million visitors doesn't amount to enough difference for any one user to notice. I'd certainly grant that. Nonetheless, it would be a strong, conspicuous gesture toward an attitude shift. Why burn what you don't have to?
From the lights out department - did you know that a cathode ray tube (CRT) monitor uses about 74 watts to display an all white web page, but only uses 59 watts to display an all black page? ...
Take at look at Google, for instance, who gets about 200 million queries a day. Let's assume each query is displayed for about 10 seconds; that means Google is running for about 550,000 hours every day on some desktop. Assuming that users run Google in full screen mode, the shift to a black background will save a total of 15 (74-59) watts. Now take into account that about 25 percent of the monitors in the world are CRTs, and at 10 cents a kilowatt-hour, that's about $75,000/year, a goodly amount of energy and dollars for changing a few color codes.
No, you won't find me leading any "Internet Goes Black" movements, but (as Treehugger points out) there are many dark colors that still represent energy savings compared to white. I spent years perfectly content with green-on-black 80x24: The screen resolution and color palettes available now offer a tremendous improvement over that.
I suppose it's possible for me to override any page's default colors, but this isn't the kind of thing that would be effective as a user-by-user grassroots movement. The hosts of the internet's most popular pages would have to buy into it.
Of course, as the world upgrades to LCD monitors, the issue may take care of itself.