If it looks something like this...
https://forums.androidcentral.com/attach...
...then it's either a loose/damaged/misaligned/not-fully-connected LCD signal cable, or a bad connector on the LCD or on the motherboard. I've also seen this effect happen if the signal cable is inserted the wrong way (e.g., the LCD end into the motherboard and the motherboard end into the LCD).
If the colors are ACTUALLY inverted there's a setting. Ggo to the app drawer and go to the Settings menu. Find Accessibility and open it. Enable Color Inversion. Once you have enabled that option, go back to the home screen. Pull down the notification drawer and open Quick Settings menu. There is a new button which will invert the screen if tapped.
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