coloring principle; pigment
Technical term used in biology and chemistry for a substance that imparts color, such as a natural pigment or dye component.
The coloring principle of this plant dyes cloth a vivid red.
Compound of 染色 (せんしょく, 'dyeing, staining') and 素 (そ, 'element, principle'). The exact historical derivation is uncertain; the term is a modern technical coinage.