A. No. With the world rapidly transitioning to LCD monitors, black-screen pages actually cause these monitors to use more electricity rather than less.
I ran a series of tests with a number of LCD monitors and the overwhelming majority of them used more power to display a black screen than a white screen.
The reason for this is that in order to show black, all of the pixels have to shut off the backlight from coming through – that requires transistors to switch on, twisting the liquid-crystal display pixels to More >