Colour Tint is a feature of iOS 10 buried so deep in the settings it was almost missed. Its quite different from NightShift mode as it acts like a red filter over the entire screen, turning all the light red.
NightShift on the other hand, removes blue light wavelengths to protect your circadian rhythm. Colour tint protects your ‘night vision’ as red light is harder to see than other wavelengths, so your eyes remain dilated – in night vision mode, and better able to re-adjust to the dark afterwards. This is perfect for a sneaky peak at your phone in the middle of the night eg. to check the time.
Here is how..
Go to Settings –> General –> Accessibility –> Display Accommodations.
Next, enable “Color Filters” with the switch at the top of the screen, then select “Color Tint” as your filter. From here, scroll down just a little further, then use the Intensity and Hue sliders to make the red effect more prominent. Both should be in the far right position for maximum redness.
Next Set up a short cut so you can triple-click the home button to turn the screen red
Go to Settings –> General –> Accessibility, then scroll all the way to the bottom and select “Accessibility Shortcut.” Choose the “Color Filters” option from the list, and you’re done. Now every time you triple-click the Home button (or Side button on the iPhone X), it’ll switch between normal screen and red tint.
Now click three times and ENJOY!