No blue or green hair

It’s worth noting that not only have humans never evolved green or blue hair, neither has any other mammal (at least that lives today). Green especially seems like it would be a great camouflage in some environments (green snakes would agree), so I wonder if there is something about hair that doesn’t ‘hold’ green or blue pigment well?

I suspect this thread will be merged, but I’ll respond here anyway.

Hair colors black through the lightest blond can be provided by varying the amount of melanin - that’s 1 pigment only. Red seems to come from some other mutation.

For hair to be able to be green or blue, it would likely require a significant mutation to provide an alternate pigment. As the column said, maybe that would require more than one mutation to work in conjunction, so is unlikely.