Question

What color light is actually the absence of electromagnetic waves in the visible spectrum, for humans?

Answer 1

black light

The visible range of light  i. e. the range of wavelengths that our eyes can detect  is a very narrow piece of the full EM spectrum. In the visible range our eyes differentiate between the different wavelengths by producing color for them. When we observe something that is green, it is green to us, because the wavelength of the light hitting our eyes is around 550 nm. If the wavelength of light is slightly larger than this it starts to look red, if it is slightly smaller it looks blue. White light is the combination of all the colors. Black light is the absence of EM waves in the visible spectrum for human beings.