Hue angle

LCh is the CIELAB colour space described by lightness, chroma and hue. In it, 0° points toward magenta-red and 90° toward yellow, and the wheel wraps around, so 355° and 5° are close neighbours. Lipstick shades cluster in a narrow part of the wheel, running from purples and plums through berries, pinks and reds to corals and oranges.

Hue angle is what this encyclopedia uses to assign undertone and, together with lightness and chroma, colour family. Shades on the blue side of red are cool, true reds in a narrow middle band are neutral, and shades toward orange are warm. The exact hue ranges for each undertone and colour family are listed on the methodology page.

Hue angle only makes sense when a colour has some chroma. For blacks, greys and near-greys it is undefined, which is why such shades are labelled neutral.