Which light bulbs give off all the colors of visible light?

Answer 1

Incandescent bulbs or if you prefer, plain old fashioned light bulbs, the ones with a filament (the bit of wire inside) that gets very hot and gives off light. They tend to give off a bit more at the red end of the spectrum, particularly the lower power ones but they do give off all the colours. Some run the filament at a sufficiently high temperature to give a pretty balanced white light. Most of the modern energy efficient bulbs give off light at a limited number of frequencies but much more light per watt of power that goes in.