Colourant

A colourant (British spelling) or colorant (American spelling) is a substance that is added or applied in order to change the colour of a material or surface. Colourants can be used for many purposes including printing, painting, and for colouring many types of materials such as foods and plastics.

Colourants work by absorbing varying amounts of light at different wavelengths (or frequencies) of its spectrum, transmitting (if translucent) or reflecting/scattering the remaining light. Most colourants can be classified as (or as containing) dyes, pigments, or some combination of these. Typically, dyes are largely translucent while pigment particles are partially or entirely opaque.

Colourant compounds can be classified chemically as inorganic (often from a mineral source) and organic (often from a biological source).

Paints and inks are colourants that are themselves usually made from pigment and/or and dye colourants, along with binders, fillers, and additional components.