Dither it! VS Dither Me This

Maybe it will be overkill for flags, but you can try with dithering algorithms, where you can select which color you want to keep: Https://ditherit.com/ Https://github.com/noopkat/floyd-steinberg. Source: over 1 year ago

ImageMagick can do anything, but it's a commandline program. There may be some websites that dither images for you - https://ditherit.com/ is one. (I also wrote a program years ago that is excellent at color reduction and dithering, but it's not currently usable.). Source: over 1 year ago

It’s called dithering. Instead of using many different colors you just choose a few and make the best of it. With using six colors (red, green, blue, yellow, white, black) any color can be matched. You can try it out with this tool: https://ditherit.com/. Source: almost 2 years ago

I used https://pixelartselfie.com/en. I later found https://ditherit.com/ which offers more features so I’ll probably do more works. Source: almost 2 years ago

Check this website: https://ditherit.com/. Source: almost 2 years ago

And if that's not enough, there's a Gameboy preset here https://doodad.dev/dither-me-this/. - Source: Hacker News / 9 months ago

If anyone is interested in playing around with dithering, I built a tool for it. https://doodad.dev/dither-me-this/ I actually wish I had Surma's article before I made it — would have given me the knowledge to add blue noise and Riemersma as options. - Source: Hacker News / 12 months ago

I used https://doodad.dev/dither-me-this/ and the 6 bit mode. Source: over 1 year ago

To make the face I used this website https://doodad.dev/dither-me-this/ and I for the icons I either googled them or just used the pencil tool. Source: over 1 year ago

A really nice page is https://doodad.dev/dither-me-this/. Source: over 1 year ago