In Yuncheng, Shanxi, there is a peculiar and popular custom. When the son is getting married, the color red or black shall be daubed to the faces of his parents. When a grandson is born, the same thing shall be done to the grandparents. Daubing red or black in such a way is in fact endued with a happy and joyful connotation.
In general, daubing red or black should be done within the same generation rather than by the younger generation. And meanwhile, it is done by a person with the same gender.
The color red or black is chosen or got casually. For example, the person to apply the color black often touches the sooty pan bottom to get the color. In order to prevent the color from being cleaned off immediately, he or she may also wet the hand with some oil beforehand. Very often, he or she will surprisingly daub the color on other's face without any warning.
No matter daubing red or black, it is often done as a kind joke and a way to increase happiness and festiveness. Such a folk custom has also distinctive local characteristics.
Source:
http://traditions.cultural-china.com/en/14Traditions4597.html
