Munsell system
A system that orders colours by hue, value and chroma, in steps that look even to the eye.
Also: Munsell colour system
Albert Munsell, an American painter and art teacher, devised his system in the early 20th century. It arranges colours in a three-dimensional solid: hue around the circle, value from black at the bottom to white at the top, and chroma outward from the grey centre. Steps were chosen by eye to look equal, so the solid is lopsided, since some hues reach higher chroma than others. Colours are written in a form such as 5R 4/14. Soil scientists, archaeologists and geologists still use Munsell charts in the field.