To start with, it is important to understand how the coloring of the people of the Shattered World came to be. Each God-King created his or her own race of followers, in his or her personal favorite color. Each colored person (that is, anyone other than a Hillman) has in his or her genetic makeup two color elements. Those that have both of the same color are generally "pure."
Any person of mixed parentage will generally be of a mixed color. These colors mix like paint most of the time, so that a cross between a Red Man and a Kyrian (the most common crossbreed) will produce orange children. The major exception is crosses between Red Men and Vashites; the Vashite green expresses as either blue or yellow in this case, so that the children have even chances of being purple or orange.
Crossbreeds are considered third-class citizens in almost all countries. Curiously, the colored races accord each other more respect than they do crossbreeds, even if the crossbreed is half-native. In other words, an Azurite will have more respect for a Zornite than for a purple person, even though the purple must be half blue Azurite.
When those of mixed parentage bear children, there is a 50% chance of each color element being inherited; so an orange woman (who are commonly prostitutes) who has a child by a Kyrian has a 50% chance of the child being pure Yellow Man. Such a child is still tainted, but he or she may move to a different area (another city, a foreign country, etc.) and lie about his or her parentage, gaining respectability.
It is a common epithet in Kyris to say "your mother is orange" as a way to start a fight, for instance.
Those who are half-Zornite are called shades. Half-Hillman, half-colored people are called fades, and as Hillmen are looked down on by the colored races anyway, fades are the lowest class of crossbreeds. All others are called by the color they are.
The one odd case is the half-Azurite, half-Kyrian cross; these people are green and can easily pass as Vashite. However, should one of them marry a pure Vashite, none of their children will be pure green; all will be either yellow-green or blue-green. Such people often attempt to pass but must avoid marriage. In Suritania, where the largest numbers of false greens are, they are called "dummies" and the penalty for claiming to be Vashite when in fact they are not is death. If they can find another false green, they have a 50% chance per child of producing green offspring, with the other 50% being either blue or yellow; but in this case they must hide these "pure" children, sometimes paying Kyrian facilitators to arrange adoptions for them.
In fact, this is one of the most lucrative and specialized of the Kyrian trades: adoption. When mixed color parents produce pure color children they may pay all they have to get that child adopted into a pure color family, for it's own good. A few Kyrian traders have made their fortunes this way.