My black cat is turning red

or so it seems! She was a full shiny black with a white star on her lower belly and a white patch on her chest. Now, the fur on her belly is turning a pretty chocolate brown/reddish color. It started around her neck, near her collar and now I noticed it is over her whole body, especially noticable when she lays in the sun! It is so beautiful, I love her coat all shiny and reddish black. Her tail, legs and head remain the same pitch black.

Do cats coats just change in color over the years? She is going on 3.5/4 years old I think and she is the only one of mine that is noticably changing color.

Isn't that a sign of a health problem?
http://www.cat-world.com.au/Black.htm

It's also listed as a sign of anemia on several websites when a balck cat's coat turns red, especially if they have worms bad enough to be causing vitamin depletion.

Not to be a wet blanket or anything, but I know you don't let your cats outside so it can't just be from the sun right?

Your cat is not turning "red". When a black cat is exposed to a lot of sun (especially one that is outside or sits a lot in the sun inside) will have a tendency to have a "rusty" coat - its that reddish/chocolate/rust color.

Those that show black cats do NOT want their cats turning rusty and keep them out of the sun for the most part. A black cat should remain black.

Now I did have a black smoke rex (father was a chocolate rex) who had a winter and summer coat. She didn't sit in the sun a lot, but during the summer her black coat did turn into chocolate - NOT a rusty color but true chocolate smoke - the hairs were brown. Never had it occur in any other of my black/black smoke rexes.

Oh wow that is really interesting. She sits in the sun all the time and occationally I will let her sit on the back patio in the sun since she likes it. As far as it being a health problem, I don't think it is in her case but next time she is into the vet I will mention it. Thanks!

Black coats oxidize really easily in sunlight. Also if the coat is excessively dry it will rust more easily, so attention to diet might be in order. And certain spray on products or shampoos for flea control will make it worse as well. Plus- laying around on carpets that cause static electricity to build up will also dry coats.
Black coats are some of the hardest to maintain in some animals.