Blue screen error The OLED screen of Samsung Galaxy Note 20 & Note 20 Ultra has a weak point that it is very easy to render the screen color. In the case of Note 20 and Note 20 Ultra, the most common shade is green.
This error occurs because the screen brightness is reduced past a certain level, when the background is showing gray tones. Both Exynos and Snapdragon versions of Samsung Note 20 phones can experience this error.
How to fix This is a software issue, which can be fixed with a factory update. In the near future, there will be a software that can completely fix this blue error released by Samsung. You can still fix it by keeping the screen brightness high. If still blue tint at high brightness then bring the phone to a service center for replacement.