The coloring agent that is mixed with a binding medium to form paint. Pigments were originally made from clay (which could be baked or ground into fine powders, such as yellow ocher), ground minerals (such as lapis lazuli, which, when ground into a powder, produces the pigment known as ultramarine blue), and naturally occurring by-products (such as candle soot, used to make lampblack).
Pigments are also made from vegetable sources (“dragon’s blood” is made from a tree bark) and animal sources (“Indian yellow” was made from the urine of cows that had been fed mango leaves).
Synthetic pigments (which are man-made) can also be traced back to ancient times: “Egyptian blue,” for example, was manufactured from a combination of copper, calcium, and sand (silica). In modern times, less expensive synthetic substitutes have replaced most naturally occurring pigments.
Source: Looking at Paintings: A Guide to Technical Terms / eds. Tiarna Doherty and Anne T Woollett. (Los Angeles: J. Paul Getty Museum, 2009), p. 59.