Nothing to worry about, not all devices have the green tint issue, apple has solved the issue for some, most likely still working on a fix for the rest, I've got the green tint issue, had the phone since launch, only seen it happen a few times, apple fixed the same issue on last year 11 models, did take them till august to fix the issue, but it was fixed in the end.
If your phone is working fine, I wouldn't be upgrading at the moment, we are 6 month away from the 12s/13 being launched.
If you need a phone now, the 12 pro max is the best phone on the market with no completion.
Best battery life
Best camera
Best video camera
Best processor
Best build quality
Miles ahead of the competition, not that I'd call the other dumb phones competition.