color line
noun [ C usually singular ] US uk/ˈkʌl.ə ˌlaɪn/ us/ˈkʌl.ɚ ˌlaɪn/ (US also color bar); (UK colour bar)
肤色障碍，种族障碍（指实行种族隔离、权利与机遇因种族而异的社会和法律制度）
a social and legal system in which people of different races are separated and not given the same rights and opportunities
Compare: Jim Crow