Oh, for heaven's sake, Fender62. Referring to someone as 'coloured' was a serious disciplinary offence (possibly resulting in dismissal) when I was teaching back in the 70s and 80s. (Any pupil using that term would certainly have been in a great deal of trouble).
Many black people regard the term 'coloured' as equivalent to using the n-word. If you haven't yet caught on just how offensive it is I can only assume that you've been living in an (all-white?) bubble for the past few decades.