And upper class people of European and native American ancestry are called "white" in many places in Latin America.

The majority and minority group, by definition are called different if they consider themselves different, otherwise there is no minority.

But consider the toy model of a society made up 90% of group C and 10% of group D. There is no discrimination, no class differences, no differential birth rates, no selection pressures, no gene expression complications, no differences in cultural norms. I don't know why in the world they call themselves C and D then or why any researcher would divide them into two groups for the purposes of a study, but lets say for the sake of argument they do.

Lets say you have X generations later, purely from a genetic perspective a 80% group C, 5% group D and 15% hybrid CD. Lets say you have x+n generations after 60% group C and 40% group CD.

Regardless of whether Hybrid group CD identifies as "C" or as "D", biologically speaking the minority population is the one that hybridised, perhaps even vanished if they where tiny enough.

The point is the minority population becomes the hybrid, and the majority population changes relatively less.