My screen turn to black and white on its own, I can’t undo it. Screen malfunction
How to fix malfunction screen. It’s turn black and white without me doing anything and is stuck. It’s hard to see
First try a Forced restart
https://support.apple.com/guide/iphone/force-restart-iphone-iph8903c3ee6/ios
Hopefully that will restore the screen, but If no better you should arrange a repair
https://support.apple.com/iphone/repair/service
Anything other than Screen or Battery may be a replacement phone and the price is in the article.
You can see additional service information within the following article:
Prepare your iPhone for packing and shipping