While latest versions of Android added a Comfort View quick settings tile, sometimes while browsing reddit at night I find that still makes my eyes hurt a little bit. Digging around a little bit, I’ve found that you can make your screen grayscale by accessing a hidden setting. First you need to Configure on-device developer options, then go to: Settings -> System -> Developer Options -> Simulate color space -> Monochromacy.
This is fine, but it would be much nicer if you could enable/disable this feature from the quick settings panel. After a bit of digging, I’ve stumbled upon the grayscale quick settings tile app which allows do you do just that: