[jeroenhd]

Back in the day before operating systems copied the feature there were tons of Android apps that added a red shift on top of your screen by drawing over other applications (i.e. https://play.google.com/store/apps/details?id=com.csk.app.sh..., https://github.com/LibreShift/red-moon). This usually breaks/doesn't work with banking apps and other such secure contexts but for most apps that's probably fine.

Sounds like you should be able to do this by just modifying Red Moon to draw a more complex overlay. If the entire screen is affected equally, the stock app may just be all you need!