To me, you, as a white guy, describing him to someone from another planet as just a creative genius, is ascribing to a colorblind society that I do not subscribe to. I find nothing wrong in telling an alien wanting to know about Prince that he was a genius and black, different in appearance from you. I think not to include his ethnicity is a nice way of whitewashing him since his descriptors would come from you, whereas I find value in our mix of cultures and would include it.
I find it fascinating and sad, and makes wonder that since Prince is certified creative genius and his ethncitiy is way down on your list in our new "colorblind" society, how quickly a movie about him will cast a white actor or closer in appearance to white to portray him, as was done to Michael Jackson, Dr. King, Nina Simone. It makes me wonder, too, how many whites are eager to remove successful PoC from their ethnicity - I don't see color - but let that successful PoC do something or is perceived to do something wrong, how swift the blackwashing appears - I'm remembering the Time and Newsweek covers of OJ Simpson, Trayvon Martin - a young pilot/astronaut enthusiast who went to space camps, Micheal Brown - bound for college; an incident in my own family that's been put to rest.
Terence McKenna said, "You could almost say that nature abhors habit, and so it seeks the novel by producing various kinds of phenomena at every level in biology, chemistry and society." So to me it would be a missed teachable-moment for the alien not to know that on our planet, nature goes crazy producing thousands, if not millions, of different types of one thing.