For unity, you can change the UI canvas to be screenspace camera instead of overlay. This means any camera effects will also effect the UI, so you can use a quantisation shader on your camera to limit it to 2 colours
Thank you very much for commenting but I am extremely unfamiliar with shaders in unity and I have no clue how to setup a quantisation shader. I looked around on the internet and couldn't find anything that I would know to be useful (I'm gonna keep looking). Thank you again tho.
