I read a post on here somewhere asking about this but can't find it now. Anyway it said that a black cat turning brown is probably due to the sun. While this is possible, according to my vet it is unlikely.The real reason is due to nutritional deficiency caused by either a poor diet, or in my case, the cat needing to be wormed. So if this has happened to your cat please make sure it is wormed regularly, and that it is fed a high quality cat food ( we feed ours Royal Canin, the vet says that is fine). Just a heads up! 