The iPhone 12 launched last October and only became available a few weeks ago. Since then, some users are experiencing display issues already.
According to this report from MacRumors, some iPhone 12 users are noticing displays with green or yellow tinting, while others are saying the some screens are flickering. The issues appear when the brightness is lowered to around 90% or below.
The effects seem to vary for from user to user. Some say it disappears after a short time, while others say it lasts longer. Still, there are some who say it is prevalent when in dark mode.
This is not totally unexpected as it looks despite how recent the device. Apple experienced the similar issues with the iPhone 11 series which has been fixed with an update.
The good news is that Apple has since acknowledged the problem, so those experiencing display issues should expect a fix soon via an over-the-air update.
For now, some users are saying that one possible workaround is to turn off True Tone, or maybe you can keep brightness at a maximum. Apple suggest to make sure to have the latest iOS version.