Artist 
Writer Pigment
A material (or colorant) that has a specific color and is used in painting. The material changes the color of the light it reflects because it selectively absorbs colors of a specific wavelength of light. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which the material itself emits light. Pigments usually have special properties that make them good for coloring other materials and generally have a high tinting strength relative to the materials it colors. A distinction is usually made between a pigment, which is insoluble in the vehicle (the material in which the pigment is mixed to make it stick to the painting support), and a dye, which is either a liquid, or is soluble in its vehicle. A colorant can be both a pigment and a dye depending on the vehicle it is used in.
See the Color Building Block for more information.