... what it is. Don't take a character and make it diverse. Just write the damn character as what you want it to be. There is no need to change or diversify a specific character but as this article points out, there is also no reason to not allow Selena's friend be blue if a blue person did the best reading for it. A role could be written as a young female American if it needs a young female American. Unless an ethnicity is needed for the role then ethnicity should not even be part of the casting description. When they are casting roles for a young woman in Wakanda, an isolated and xenophobic and secretive nation in Africa, then it would be justifiable to ask that she be be an African but changing a written character's ethnicity just to diversify the movie is wrong.