A genuine mistake is a genuine mistake. If there is no intent to offend then simply be prepared to apologise and change the terminology you use accordingly. Although I must say that the term "coloured" has been frowned upon for a few decades now so there's not much of an excuse other than being completely out of touch for a long time.
That's for regular people in their day to day lives. For people in a position of power who face public scrutiny, it's their responsibility to make sure they are up to date with what is deemed as acceptable. It's not really difficult.
Personally I don't use either terminology just pointing out that using similar words in different order can lead to offence.