Screen display

Reset PRAM:  Reset NVRAM or PRAM on your Mac - Apple Support

Some display settings are stored in PRAM.

Reset  SMC:   How to reset the SMC of your Mac - Apple Support   Choose the appropriate method.

Startup in Safe mode. https://support.apple.com/en-gb/HT201262

To leave Safe Mode, click  in the menu bar and choose “Restart”

Starting up in safe mode usually resolves minor software glitches.

mel_kate wrote:

I have the MacBook Pro 13-inch, 2017. Two days ago I opened it and there's a grey tinge over the screen. For example, when I have a white background and open finder the inside of finder is a grey/green colour and the outline of finder is like a grey/green shadow (as per image). It is also a grey/green at the top of my computer. It happens on any screen and makes pictures look funny. I know that it must be a display thing but why has this happened and what do I do? Would it be a free fix if I went to apple considering I haven't done anything to cause this? Thanks :) Mel

https://discussions.apple.com/content/attachment/3ac52f0c-4289-40aa-bd7d-b05158e0eaa3

Does this computer have TrueTone color correction— you can try toggling that option on/off

Use True Tone on your Mac - https://support.apple.com/en-us/HT208909