Give the spec I wrote a shot.
Just 15 or so hardcoded colors: https://github.com/coracle-social/flotilla/blob/68ebd32e1500bc5a6ac9f5e23c3ed66ea25ca55d/src/app/state.ts#L123
I've used HSL in the past, but never was very happy with the results
Discussion
The first color I see is unfortunately not usable in Light mode.
The one for my own pubkey, neither.
Also, why not use the full HEX pubkey to avoid weird or repeating colors with mined keys etc?