BlinkPosterize

If you also do think that posterize node tend to damage the colors of your image. This blink is for you !
You have a colorpalette (can be your image downscaled and well pixelated (filter impulse?)), and for each pixel of your base image, it will replace it by the one that has the nearest color in the palette.

As it checks all pixels of the palette, the bigger it is, the slower the blink will compute !
I let everything open to be edited so you can learn too. I'm not a professional coder, it works but it's perhaps not the cleaneast blinkscript ;)

Have fun with it !

A little thank you is always nice in the comments if you like it and or use it !