i downloaded the whole medium app just to comment on the last part of your article, which is a great piece of work i must say, even though i’m not a developer i can still keep up with it.
there is actually an easy implementation for daily usage. I use it on a daily basis for the battery (iphone x) and revert it back when apps/games don’t support it. Settings > General > Accessibility > Accessibility Shortcut > Smart Invert Colors. I use it on the Assistive Touch, setting the Single-Tap action to Accessibility Shortcut, i’m only one tap away from smart invert. it’s super neat but doesn’t quite get the exposure it deserves