Hey, thanks! I used shaders to limit colors. It is the combination of depth-based edge detection and dithering algorithm with random texture for the pattern. I made the shader public: https://gist.github.com/kerniee/77733053a832749fa62e10af2e4c3de0
I followed this godot tutorial to setup full screen shader: https://docs.godotengine.org/en/4.4/tutorials/shaders/advanced_postprocessing.ht...
There are better techniques for dithering, but i had limited time to experiment with them, so my implementation is not so advanced, but it works