Display technologies that light up are all based on RGB, as far as I know (additive color). Printers and such, which use subtractive color, would use CMYK. Wha

Display technologies that light up are all based on RGB, as far as I know (additive color). Printers and such, which use subtractive color, would use CMYK. What takes more power depends on the hardware. An OLED display would take more power to light up a pixel than to keep it dark. An LCD display would typically take slightly more power to show a dark color. The backlight is always shining (which takes most of the power), but darkening an LCD pixel takes more power than just letting the light through does. Maybe the actual power savings would come from lighter rendering calculations (only having to calculate a single color channel)?