What is Hue?
The named color of a sample — red, blue, green, etc. The H in HSL/HSV color models. Independent of saturation (purity) and lightness.
In detail
Hue is the dimension of color that gives it a name. Pure red, pure orange, pure yellow are different hues. In the HSL color model, hue is expressed as an angle from 0° to 360°: 0° red, 60° yellow, 120° green, 180° cyan, 240° blue, 300° magenta. In CIE-LAB, hue is implicit in the angle of the (a*, b*) point. Designers use hue separately from saturation (purity) and lightness because the three respond differently in print: hue tends to be reproducible across substrates, saturation drops on absorbent fabrics, lightness is affected by ground color showing through. Hue is the most psychologically loaded color attribute — color associations (red = energy, blue = trust, green = nature) are largely hue-driven rather than saturation- or luminance-driven. Textile palette design typically starts with a hue selection (warm tones, cool tones, complementary pairs) before refining via saturation and luminance for the final spec.
Example
Three swatches with the same hue (red, ~0°) but different saturation: vivid red (90% sat), dusty rose (40% sat), pale pink (15% sat). All three are 'red' but read very differently on fabric.