Pigment is a gene that determines what color overlays the original sprites that make up a creature's body. The pigment system grew more complex and added more visual assets through each game in the Creatures series.
In Creatures 1, pigments were controlled by a single type of gene that controlled red, green and blue pigment values and could not be activated at different life stages, despite the gene providing that option. One of the first genetic breeds, the American Cardinal Norns, had sex-linked pigment genes, leading to males being born with a red pigment, and females being born with a green pigment.
The Life Kit added an additional pigment bleed gene type, which applies TINT transformations to the creature's sprites. This feature was not documented, and they cannot be inserted into a genome without the use of a hex editor. In the later games, pigment bleed genes are found in the standard creature genome.