HOW TO USE NIGHT SHIFT ON YOUR IPHONE
Released in iOS 9.3, the Night Shift feature in iOS allows you to filter out blue light and adjust the warmth of the colors in your display. To turn it on go to:
Settings > Display & Brightness > Night Shift
There is an option to select the hours that best suit you. You can also choose Sunset to Sunrise to have iOS pick hours automatically based on your location.
HOW TO USE NIGHT LIGHT ON YOUR PIXEL PHONE
On Google’s Pixel phones and some other stock Android devices running Android 8.0 Oreo and later you can find a blue light filter option here: