Pigment

Powder used to add or alter colour

A pigment is a chemical compound that gives a substance or organism color, or is used by humans to add or alter color or change visual appearance. Pigments are nearly or completely insoluble and chemically unreactive in water or another medium; in contrast, dyes are colored substances which are soluble or go into solution at some stage in their use. Dyes are often organic compounds whereas pigments are often inorganic.

From Wikipedia, under CC BY-SA. More on occurri.