Deep Purple is a cat seen in the first book and movie. He was one of the victims of Claudandus's plan.
Deep Purple's corpse is only seen after Bluebeard informed Francis of the new killing. While observing the scene, Francis suspected how (despite his age) the old cat was still interested in females and that was the reason of his death.
Francis has a brief meeting with Deep Purple when he is still alive (differently from the movie) and the old cats cry aggressively for his territory. Deep Purple's corpse is seen (like in the movie) but after Francis and Bluebeard find his corpse, Francis has a nightmare, where Deep Purple is throwing kittens at a garage door.