Karun is, but Anthony isn't surely? He looks British English to me?
A "colour commentator" in the sense of an expert who describes the intricacies of the sport in finer detail (compared to the main commentator, who tends to announce what is happening), not in the sense of race or ethnicity.
Yes. the norm practice is for a "colour" commentator to back up a main commentator. Brundle is fine, and doesn't need to be replaced by Ant or Karun, but interestingly I've noticed Karun trying to do both. And not bad either, if he could be told to stick to just one style, ie the main.
Edwards is now too shouty. He best works off a script, given the reviews.