Is white or black really a color?

Black and white are generally considered colors.

However, technically speaking:

In art, white is the absence of all color and black is the presence of all color. To artists, black is considered a color, white is generally not.

In light, the opposite holds true. Black is the absence of color, and white is the presence of all color. To scientists, white is a bunch of colors, and black is not.

So the answer to this question really is, "it depends on what your perspective is".

Many consider white and black to be shades, as opposed to colors. The mind picks them up as unique colors as opposed to say blue, but without blue, or blue in light.

Color is only something that exists in the mind of the perceiver.

Explanation...

Color is the reflection of particular portions of the light spectrum. Red, Orange, Yellow, Green, Blue, Indigo and Violet. The colors that can be seen in a pure rainbow. These reflections are picked up by the optic nerve and translated by the brain into the "colors" we all know.

White is the reflection of ALL the colors.

Black is the reflection of none. When one perceives black there is no perception at all.

Example. If there is a picture of a flag, green stripes next black next to yellow, you see the green and the yellow but you do not see the black. It is nothingness. But since you see the yellow and green in contrast then the black appears to be there.

To sum it up...

White is NOT a color but an equal combination of ALL the colors of the visible light spectrum.

Black is NOTHING but the comparative perception of the surroundings. It can not be seen.

When all the colors are combined, it makes white. As an example. "White" sunlight when refracted identifies its component colors. These colors are Red, Orange, Yellow, Green, Blue, Indigo, and Violet. If you were to take these colors on a wheel and spin the wheel, you would see white.

Black is considered the abscence of color.

Black can be defined as the visual impression experienced in directions from which no visible light reached the eye. That's what I found on Wikipedia leading to my other answer.

The color white has all the colors of visible spectrum.
https://en.wikipedia.org/wiki/White

Black and white are values.

http://www.colormatters.com/vis_bk_white.html

The classification of black and white as colors depends on the context. In art, black is seen as a color because it's the presence of all color, while white is the absence of color. In the science of light, however, this is reversed: white is considered to have all colors as it comprises all hues on the light spectrum, and black is seen as the absence of light and color. So, whether black and white are considered colors can depend on whether you're looking at it from an artistic or scientific perspective.