Not all people of colour are the same and neither are all women. So if there are people out there that want to play a character but are afraid they won't sound "black" enough or that the female character they are writing sounds too "man-ish" I'd suggest they chill. Chances are you're probably worrying too much. Even if it is for the most benevolent reason possible.

Shakespeare never left England and you never hear people complaining that his Danish, Roman, or Venetian characters weren't authentic enough.