Save energy searching the net
"Image displayed is primarily a function of the user's color settings and desktop graphics, as well as the color and size of open application windows; a given monitor requires more power to display a white (or light) screen than a black (or dark) screen." Roberson et al, 2002
The savings are tiny, but many tiny savings can make a big difference. In fact it is theorised, using total page views and the fact that a white page uses about 74 watts to display while a black page uses just 59 watts that the savings could reach 750 mega-watt hours a year.
Another important spin off is each time an individual uses the search page they are reminded of the importance of saving energy.
Why not do your little bit?