yes, colors can be minted, and they are only useful to the extent you remember the colors of the people you are following. I could probably remember 20 or 30, so not really useful.
The whole point of a follow is that you don't have to remember anything about them. That's why you literally bookmark them.
Colours are useful: - to find yourself - to find someone new (I'm pippelina. Pink pippelina 😎) - for imposter detection services (If pfp, bio, last digits of npub, color, ... match with an earlier created profile)