Youh'Kai skin pigmentation works basically the same as it does in humans, with only two significant differences.
For one, the Youh'Kai have four instead of two pigments. So in addition to the human red/black and yellow/brown, the Youh'Kai can have green/gray or white/blue pigments, of which the last is a very rare coloration that carries cultural connotations of either nobility and enlightenment or savagery.
Of those four possible pigments, each individual carries only two, one of which is always dominant. This means that unlike humans with their infinite shades, there are clear groups of skin colors among the Youh'Kai.It is possible but rare for a Youh'Kai to have the same pigment twice.
It is important to note that the white pigment some Youh'Kai possess means that their skin color is opaque even if pale, giving them a queer make-up look in the eyes of humans.