If anything, dark background will use more power as the pixels need to be fully powered to block out the backlight. Not sure if this is still the case, but it u

If anything, dark background will use more power as the pixels need to be fully powered to block out the backlight. Not sure if this is still the case, but it used to be afaik. CRT's were the opposite in that black meant the beam was off or somesuch and therefore white used more power. But that's not been true for a long time.