I use something like "zir cheeks turned red" or "zir face became pink" or "blossomed pink/red" and things like that.

He's stopped vomiting, I should've clarified that. Now he's just tired all the time. Dad felt his stomach to see if he'd yelp in pain or anything like that, and he hasn't responded, so it doesn't look like there's anything sharp stuck inside him.

The essays are going to be such a pain. D: