Color and mix are two attributes of graphics primitives. They can be specified by an application in a number of ways, and are specified in the ...BUNDLE data structures associated with the five graphics primitives and in bit maps. Bit maps and some of the primitives have both foreground and background color attributes. For example, a character string primitive has a foreground color attribute that specifies the color of the character and a background color attribute that specifies the color of the character cell surrounding the character.
The mix attribute controls how each primitive is combined with the existing drawing. Among other things, it affects the color that results when primitives of different colors overlap. Primitives with foreground and background color attributes also have foreground and background mix attributes.