Never seen purple kribs myself other than the belly area of the females looking purplish. Though I think there are at least 3 colour types I have seen. One is yellow which seems most common. The gill plate and horizontal bar on upper body shows yellow. Then in UK here I've seen blue, which is guaranteed to be aquarium strain colour. Then for both there are some males that have red gill plates. These are shown in the book by Anton Lamboj which people interested in west african cichlids should get I believe. I myself have a small colony of P. pulcher at home in a 4 foot tank with 3 generations inside...initial parents, their fries and then their grandfries :P Only a total of 3 males though so far. Must be my pH.