What is the systematic mistreatment of members of a group based on the color of their skin called?

The systematic mistreatment of members of a group based on the color of their skin is called racial segregation.

Explanation:

Racial segregation is the separation of different racial groups in daily life, whether in restaurants, cinemas, bathrooms, schools or when buying or renting houses. Segregation may be dictated by law or may exist through social norms. It is maintained in various ways, whether it is discrimination when hiring a person for a job or renting a flat to people of a certain race, to violence.

To discriminate against someone with the reasoning of inferiority due to the color of their skin is called Racism.