Hue is one of the main properties (called color appearance parameters) of a
color, defined technically (in the
CIECAM02 model), as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as
red,
green,
blue, and
yellow" (the
unique hues). Orange and violet (purple) are the other hues, for a total of six, as in the rainbow: red, orange, yellow, green, blue, violet. The other color appearance parameters are
colorfulness,
chroma,
saturation,
lightness, and
brightness.