Yup, like Rukbat says, the blackest the better (note that for AMOLED to really save power the pixel has to be pitch-black as that's the only way it'll be turned off; if it's just a dark color, but with color nonetheless, the pixel is still on).
That's why one of the Battery Saver features is to turn your phone into a black-and-white retro version.
How does one go about turning it into a black and white version? I've got a complete black background currently but would like to expand on this!
what is the best theme for battery consumption?
any themes that have a lot of black backgrounds to save battery power?