Blackle vs. Google Monitor Power Consumption Tested

Is the search page, Blackle.com, really an energy efficient alternative to Google? The theory is websites with black background save energy. That claim is based on an assumption that "a given monitor requires more power to display a white (or light) screen than a black (or dark) screen. Is this a blatant green washed marketing ploy, or an earnest energy saving tweak for something we use every day? ... PCSTATS