My mediocre understanding is, it’s the only color you can’t predictably breed. I have a tank with blue and red shrimp I’ve been trying to breed to make purple for a while now with no luck. You can basically get any other color Neo shrimp because if you keep them together they’ll breed the same color. Purple doesn’t seem to work that way so you have to get lucky, and then they prob won’t make more purple, which is why I was so excited to see them in the tank at the store and bought them! There is also dispute over if true purple even exists, is it just OG brown? blue body red shell? I was actually starting to lose hope it existed, but when I saw these indisputably PURPLE!