I made this simple tool to try out extension icons and colors for your Flarum extensions
https://ext-icon-gen.flarum.dev/
Click on the lock icon if you're happy with a value, then the randomize button will only cycle the other fields.
The (readonly) field below the tool let you copy-paste the content directly to your composer.json
file.
You can also use it to get inspiration for some extension ideas with the random extension name generator.
It's completely client-side. The source code can be found here https://github.com/clarkwinkelmann/flarum-extension-icon-generator
Let me know what you think!
If I find the time I'll try to add an icon search/picker and maybe try to get another library that gives even better colors.