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Black is an abscence, meaing abscence of color.
Each color had a wavelength of frequency and "black" doesn't reflect any wavelength of colored light.
At night, without light, you can not see color. You see objects and shades of darkness.
Color blind individuals may see in black and white or some see some colors, such as the ones that can not distinguish between red and green, they look gray.
In other words, black is not a color.