Do you want to turn your iPhone screen red and protect your body clocks from 100% of damaging blue and green light?
Then here's how!
Selecting the red colour filter
Go to Settings –> General –> Accessibility –> Display Accommodations. Here, you will find "Colour Filters" option. Select it.
Next, enable "Colour Filters" with the switch at the top of the screen, then select "Colour 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
Creating a shortcut
It would be a pain to be doing the red colour selection each evening, but fear not, we can add a short cut
Go to Settings –> General –> Accessibility, then scroll all the way to the bottom and select "Accessibility Shortcut." Choose the "Colour Filters" option from the list, and you're done. Now every time you triple-click the Home button (or Side button on newer iPhones), it'll switch between normal screen and red tint.
Lets hope other phone companies follow suit with this like Samsung as currently you can only create a warmer colour which is not as optimal as the iPhone