Problem with iPhone 7 Plus display! Colors become change:'(

settings->accessibility->Increase contrast

and other settings in there is what I would try

otherwise it could require repair and your warranty would only be

valid in country of purchase

Hi

You may be referring to Night Shift mode.

This automatically adjusts the display colour after sunset, making it easier on your eyes and avoiding exposure to bright-blue light, which may make it harder to fall asleep. The display returns to the regular settings in the morning.

To disable or adjust the settings for the feature:

• Swipe up on the display to open Control Centre > tap the Night Shift icon (shaded sun) to turn the mode on or off.
• Go to: Settings > Display & Brightness > Night Shift - including to schedule the setting and/or adjust colour temperature.

More information:

Adjust the display settings on your iPhone, iPad, or iPod touch - Apple Support