Last week, how to geek ran a short piece on pixels in amoled screens and battery life.
HTG Explains: Does Plain Black Wallpaper Save Battery on Mobile Devices? - How-To Geek
Bottom line: black on amoled screens don't illuminate pixels and therefore don't use any battery juice. White or any other color does illuminate pixels and, hence, uses up battery power.
I tried it. Unfortunately, it works. Switching from my gorgeous and grey monochrome wallpaper back to a black background has returned my battery to its previously long-lived self. No, I didn't use a meter, so no screenshots, but try it yourself and see what happens.
I say unfortunately because I love visually arresting home screens. At least now, I can make an informed choice.
Sent from my unrooted 32 GB Polish Samsung Galaxy GT I9300 running 4.1.1.