Person of color. Used as a distinction due the perceived user base here being mostly white males. It’s a common term.

And now that you know the meaning you’ll be seeing it every where... Baader Meinhof phenomenon and all that.

Oh, thanks.

Maybe. (I certainly do experience that in general!) In the UK though I very rarely hear people describe themselves or others as 'a person/people of colour' though, even in full I mean; it's American to my ear.