Two things:

1. As an addendum, wait to send that email. Not to say don't send it, but if you wait, go back and review what you've typed later, you might realize that you want to swap out some words to be less confrontational, or be a bit more constructive to work toward a solution. Worst comes to worst, type it out in the moment, go for a walk, come back to reread it later and see if you still want to send it the way you originally wrote it. Can make a frustrating situation much more productive. Same principle for confronting someone in person if that's more your thing, just take a minute to process and think about how you want to confront them.
2. If a person of color seems to snap out of nowhere at you, or it looks like they're overreacting at something that you've done, consider that there's a decent chance you've been committing a microaggression at them, and they've been contemplating how to respond for a while. It very well could be the type of thing that seemed small in the moment, they didn't want to come off as "the angry minority" stereotype, and after the 100th time you did it they snap. For people of color, we often have to wrestle with how to confront people in the moment over racial microaggressions because we don't want to be seen as complaining over every little thing, especially in the workplace. So we often feel like we have to let it slide each time it happens, but at the same time you're still dealing with something slightly racist from someone you see regularly. Understanding goes both ways on this one.