"... a given monitor requires more power to display a white (or light) screen than a black (or dark) screen"and that if the Google search page was black then something like 750 Megawatt hours could be saved per year ... and thats a lot, isn't it? (I don't pay the electricity bills in my house so I have no idea.)
Possibly I also have no idea because the language of ordinary life has become so confusing lately ... there's numbers like megawatts, incomprehensible carbon calculations, offsets (what the hell is an offset!?), there's parts per million levels of all kinds of stuff in the air, the water, the blood, and in huge pools of industrially farmed pig shit, there's global exchange rates, trade deficits, floating interest rates, and industrial averages. What's a poor boy to do? Yea, yea ... I know ... Wikipedia yadda yadda yadda.