How the heck is that accomplished? In this present age of oddball colors (mostly done by anodizing or cerakote) that might actually be popular.
The gunsmith said it was not kept in the bluing bath long enough. Who ever did it took it out too soon. He really thought it was a "Lunch box gun" that someone accidentally got into the shipment. That's an unauthorized gun an unqualified workman was building for himself to sneak out of the factory that somehow got put into the official factory product queue.
I have several old guns that the bluing has turned purple. None of them are new, but several of them are Colt. I suspect that the bluing neutralized properly after it was blued.
Interestingly, it usually is not the entire firearm. One part (or maybe two) is usually purple with the others remaining blue (such as the barrel being purple while the frame and cylinder are blue, etc).