What 2 things give off light? What 3 colours make white lght?

Answer 1

M Trespassers is quite right that mixing blue green and red lights in the correct proportion will give you white light (so will mixing magenta,cyan and yellow).

But photons don't give off light - they _are_ light and I'm not really sure that electrons are the answer you are looking for either. Don't get me wrong, they may be two good answers, it's just that I'd be uncomfortable with them without making a bit of an effort to find out why..

Answer 2

Red light, blue light, and green light mixed gives you white light.
Electrons and photons give off light.