There exists some correspondence, more or less precise, between hue values and color terms (names). H r g b = a t a n ( 3 ⋅ ( G − B ) / 2 ⋅ R − G − B ). To place red at 0°, green at 120°, and blue at 240°, Preucil describes a color hexagon, similar to a trilinear plot described by Evans, Hanson, and Brewer, which may be used to compute hue from RGB. Hues are first processed in the brain in areas in the extended V4 called globs. In painting, a hue is a pure pigment-one without tint or shade (added white or black pigment, respectively). Exceptions include brown, which is a dark orange. Usually, colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness, such as with "light blue", " pastel blue", "vivid blue", "cobalt blue". The other color appearance parameters are colorfulness, saturation (also known as intensity or chroma), lightness, and brightness.
Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a color space coordinate diagram (such as a chromaticity diagram) or color wheel, or by its dominant wavelength or that of its complementary color. In color theory, 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, orange, yellow, green, blue, violet," which in certain theories of color vision are called unique hues. The hues in this image of a painted bunting are cyclically rotated over time in HSL.