Changing color?!?

My cat Boots has recently gotten white patches of fur on his side. He is a tuxedo rescue cat and is about 9 years old. Below is a link to some pictures of him. I know he is overweight... Any explanation??
http://s1091.photobucket.com/albums/i400/kdurheim/

I have no idea...
How old is he? I know when we had a rabbit as he got older he 'grew' more spots..

He's probably just going 'grey' animals do it just like humans, just more noticable on some.
My tortie got more red with age and her black turned brown.
My black dog is getting a few white spots as well as white on his muzzle.
My dog before him was mostly white with some black spotting, as she aged, she developed more black spotting.

I don't think I'd be overly concerned by it, but if it would ease your mind, perhaps a call to the vet to ask about it will help?