The thing is, words like "black" or "colored" can be offensive to them since many people have used those words back in the days when people discriminated them. Pretty blonde and pretty brunette are not exactly considered offensive. Pretty colored chick, on the other hand, can come off as offensive and racist. And you don't need to be racist to come off as offensive. For example, you're not going to walk up to some fat lady outside and say, "Hey, you're a cute fat chick!" The reason is, people use "fat" as a way of insulting others sometimes. So, same with "black" or "colored." Those words are considered to be racist and offensive words, so even if one does use it to compliment, they can take it the wrong way.