Inverted color

If Smart or Classic Invert is turning on your iPhone even after you have turned it off though this is strange but you may try some of these...

1. Restart your iPhone: Sometimes, a simple restart can fix issues like this.
   1. Restart the device. That's it.
   2. Still not solved --> Force restart iPhone - Apple Support
2. Reset All Settings: Resetting all settings on your iPhone can help fix software-related issues. Go to Settings > General > Transfer & Reset > Reset > Reset All Settings. This will reset all your settings to default, but it won't erase any of your data. All settings—including network settings, the keyboard dictionary, the Home screen layout, location settings, privacy settings, and Apple Pay cards—are removed or reset to their defaults. No data or media are deleted.
   1. Reset All Settings: Return iPhone settings to their defaults - Apple Support:- Return iPhone settings to their defaults
   2. You can return settings to their defaults without erasing your content.
   3. If you want to save your settings, back up your iPhone before returning them to their defaults. For example, if you’re trying to solve a problem but returning settings to their defaults doesn’t help, you might want to restore your previous settings from a backup.
3. Update your iPhone: Make sure your iPhone is running the latest version of iOS. Go to Settings > General > Software Update and check for any available updates.There are only 2 ways to update an iOS/iPadOS. Know how to...
   1. Update Over-the-Air (OTA) —> Update your iPhone or iPad - Apple Support (IN)
   2. Update using iTunes/Finder —> Update your iPhone, iPad, or iPod touch - Apple Support (IN)

If none of these steps work, it's possible that there is a hardware issue with your iPhone's display. In this case, you may need to contact Apple support or visit an Apple store for further assistance.

Please check if you are using Classic Invert.

Please see the pic below