A Hue is a color of the rainbow.
They can be highly simplified as being the color name that gives a particular wavelength (then without white, black or gray)
It is one of the main properties describing a color
The average person can distinguish about 150 colors (hues) of light.
Every one can be described using one or two of only 6 (7) colors :
This colors as in the rainbow are defined as pure hue (ie without any admixture of other colors).
The human perception distinguishes between:
Technical definition (in the CIECAM02 model): the degree to which a stimulus can be described as similar to or different from stimuli that are described as the unique hues (red, green, blue, and yellow).
Different hues can be obtained by mixing two primaries, two adjacent colors or two complementary colours in equal or unequal proportions.
See Color - Chroma:
Hue scale in the HSB/HSL encodings (representation) of RGB
A color wheel is an abstract illustrative organization of color hues around a circle. Each angle corresponds to a hue.
The variation that you see regularly in color intensity between the center and the edge of the circle is due to a saturation variation (not to a hue one).
See also the hue saturation value cone.
A unique hue is defined as a color which an observer perceives as a pure, without any admixture of the other colors.
The unique hues are :
To remove the hue of a color and get an achromatic color (greyscale color between white and black), you mix the color with its opponent color.