I had a similar problem on my ipad air 2. Cause of the problem: bad battery; after 4 years, one of the batteries in the pack start to swell (developing gas). the swollen battery put pressure at the screen, resulting in weird colors (like inverted coloring). fixed it temporary with playing with the white color setting, however this increases battery usage and I believe heats up the airpad more, potentially damaging more components. Another fix on youtube is dropping your ipad or hitting it on the back. I believe at least the latter solution would be pushing out the gas from the battery, so it is not swollen anymore. However the gas is toxic, and the battery outershell will be torn, potentially allow leaks from the battery. If you encounter this problem someone should take off the screen (very carefull to not damage it) and check the batteries for swells and if so, replace battery. Cheaper fix than replacing the screen.