cat changing color

I have a 1 1/2-year-old male black-and-white tuxedo cat. In the last couple of months he's started changing color. The black is turning gray underneath, and now only about 1/2 inch on the ends of his hair is black. It looks like he's dyed his hair and needs a touch-up on the roots. This is not an undercoat -- it's his regular coat. The white on his throat, tummy, and feet is still white. I've had cats all my life and have never seen anything like this before. Does anybody have any idea what is causing it?

Thanks for any help.

Betty

I would see a vet .. My Zoey is still changing but she is a red head and they are slower to color

It may be to do with the time of year. My dad has a blue persian, and every summer his lighter coat comes through and he looks almost brown in places.

You probably didn't notice it last year because he still had his kitten fur

Sounds like he's turning into a smoke color. My understanding is that smoke coloration isn't always apparent in a younger cat, and can develop as the cat ages.

Little bit of additional info, this is from the CFA website:

Smoke - Often difficult to tell from solid color kittens except that smokes sometimes have white around the eyes and a paler stomach. May take some months to tell which kittens will be smoke because the full coat color is sometimes not seen until the adult coat comes in at 2 years. Undercoat begins to show at 3 weeks, and by 6-8 weeks have a mottled look.

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And a definition of smoke coloring this is from fanciers.com :

If your cat is pretty much solid black or gray, but the roots of the hairs are distinctly white, it is a "smoke." (It's normal for the roots on a solid cat to be grayish; true smokes, on the other hand, have definite white roots.) Smokes are the solid version of silver tabbies. These cats are very dramatic because when they move, the hair parts and the white undercoat can be seen.

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Thank you so much for this info. This sure sounds like what he is turning into. His father was a pedigreed cream Persian, and his mother was Himalayan (mixed), so there's no telling what in the world kind of genes he has.
Betty