Open Settings
Tap Display & Brightness
Tap Night Shift
Turn on Scheduled or manually enable it
Adjust the color temperature toward More Warm
Open Control Center
Press and hold the brightness slider
Tap Night Shift to turn it on or off
Go to Settings
Tap Accessibility
Tap Display & Text Size
Turn on Color Filters if needed
Select Color Tint and adjust warmth if you want a stronger blue light reduction