The iPhone 8 uses a True Tone display that looks loads better than a standard iPhone 7 display. This is an iPad feature that came over to the iPhone 8 and iPhone 8 Plus.
You may have turned it on when you setup your new iPhone, but I've found many users skipped it because Apple didn't explain it enough during the setup and they couldn't use the phone to search for more information.
The True Tone display shows a better looking screen based on your lighting situations and it means the whites on the screen will look more realistic when reading text and using apps.
To make sure this is on open Control Center -> 3D Touch into Brightness -> set True Tone to On.