Thank you Cara and Jon!
I have requested a picture and copy of the receipt from the tenant, and also asked whether the new door matches the other door (there are 2 garage doors on the house). I will be sure to check for any warranty and to get a copy of the claim info.
I'm not sure they were trying to hide it necessarily, it feels like they wanted to get it handled before telling us about it, perhaps so we wouldn't think they were going to drop the ball or trying to dodge the issue. They just moved in a few months ago and they've otherwise been very good tenants. I will definitely let them know to contact us before any future repairs though.
Unfortunately, we don't know the brand or type of paint since it was painted by the previous owners. I think they may have to just have the color matched. Fortunately it's a stand alone door with faux brick on the adjacent walls, so there's no identical paint color right next to the door, so hopefully color matching will be sufficient for people to not notice the difference.