Chosen Solution
I did a screen replacement on my iPhone 6s a few days ago successfully. The camera worked fine for days until I was in a facetime call with my friend and they said that my camera was showing pink and then froze. I closed the app and restarted the phone and went to the camera app to a black preview on both cameras. If it means anything, the battery on this phone is pretty decayed and has also been shutting down randomly for a while. I updated the phone to the iOS 11.3 beta 6 and it didn’t fix any of the issues so I’m contemplating buying a new battery.
It could simply be loose wiring when you replaced the phone screen. Open it up and recheck everything is connected properly and it wouldn’t hurt to clean the contacts to make sure they dont have residue (from fingers and such) on them.
