Q: screen color

Hi

You may be referring to Night Shift, which changes the colours on the display to the warmer end of the colour spectrum, to make viewing the screen easier on your eyes when it’s dark.

If you schedule Night Shift to turn on from sunset to sunrise, your iPhone will use time and geolocation data to determine when to turn on and off.

If you would prefer to disable the feature, go to: Settings > Display & Brightness > Night Shift.

More information:

http://help.apple.com/iphone/9/#/iph60ba71065

http://www.apple.com/ios/updates/