Not sure why something being outdated suddenly makes it racist? It's not like it's "the N word" which was mostly used as a slur and so obviously is not acceptable... "Coloured" is just "old fashioned", I don't really understand why it's supposedly offensive. As far as I know, the word hasn't really been used in a derogatory context in the past?
If anything, looking at it logically, "black" should be offensive! Very few black people are even close to having a skin tone that is actually "black"... it sort of seems like a massive generalisation to me... to say that just because someone has a darker skin tone they are "black"
sort of sounds a bit racist