When a character has two or more distinct colors making up their layer of skin.
This doesn't include naturally occurring differences in colors such as areolae, nipples, bruises, and blushing to name a few. The skin colors have to be unnaturally colored and visually distinct from each other. For instance, post #472760 has blue skin and red skin divided evenly on her flesh.
This tag implicates multicolored (learn more).