I do this too on my iPhone - like all the really good iPhone settings, it’s an accessibility option, under Display -> Color Filters. You can also set up the “ac

I do this too on my iPhone - like all the really good iPhone settings, it’s an accessibility option, under Display -> Color Filters. You can also set up the “accessibility shortcut” so triple-clicking the side button enables or disables it. It really reduces the intensity of the phone - you never realize just how garish the color choices are for almost every app out there until you see it in B&W.