I've definitely seen it used for non-white coworkers and coworkers from other regions, but typically in the context of relocating for corporate work.
But then, I worked for a western corpo but with a ridiculously diverse group of people during that time.
We had enough of them at a time that "the expats" was a relevant group of people you needed to refer to for specific things. Language lessons, HR support, what have you. I definitely heard the anglo guys refer to themselves as that frequently, and that then became the word people used.
I had a chip on my shoulder about telling people I was a migrant, but I was pretty alone on that. The anglo guys mostly said they were "expats".