Hue

[3] In painting, a hue is a pure pigment—one without tint or shade (added white or black pigment, respectively).

[4] The human brain first processes hues in areas in the extended V4 called globs.

In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as the CIE 1976 (L*, a*, b*) (CIELAB) and 1976 (L*, u*, v*) (CIELUV) color spaces, hue may be computed together with chroma by converting these coordinates from rectangular form to polar form.

Specifically, in CIELAB[7] while, analogously, in CIELUV[7] where, atan2 is a two-argument inverse tangent.

To place red at 0°, green at 120°, and blue at 240°, Equivalently, one may solve Preucil used a polar plot, which he termed a color circle.

[8] Using R, G, and B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, and B prevail, then apply the formula given in the table below.

This is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction.

[10] Hue angles computed for the Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° (red, yellow, green, cyan, blue, magenta, and the colors midway between contiguous pairs) and differ by approximately 1.2° at odd integer multiples of 15° (based on the circle formula), the maximal divergence between the two.

The process of converting an RGB color into an HSL or HSV color space is usually based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone, or the HSL double cone as a double hexacone.

On a chromaticity diagram, a line is drawn from a white point through the coordinates of the color in question, until it intersects the spectral locus.

There exists some correspondence, more or less precise, between hue values and color terms (names).