Mine are a mutation from my cherries, I have them in a planted tank with lots of tetras and runny nose tetras... Why I mentioned the fish? Well, the red cherries really pop nicely with the black soil and background and well are harrased by the fish to the point that they are disappearing from this tank, on the other hand the purple/black are just ok with them I think is hard for the fish to see them, they are multiplying. Is there a way that this mutation is a way of survival? They are adapting to the environment around (changing color)? This Is something that I have in my mind for a while.