This is Puff, who has to be nearly 20 years old. My mother hand-raised Puff when she was still able to get down on the floor and play with kittens. Since Mama died in 2004 after a long illness, I know Puff is not a young cat.
No, she is not grey because she is old. She has always been a grey cat with a little yellow in her. Mama used to call her 'a beautiful puff of grey smoke'. Puff is just as cranky as she looks in this picture. Hand raising a kitten, though sometimes the only possible course, has certain consequences. For one thing, mama cats do teach their kittens, and rough housing with siblings teaches them how to fight.
Puff picked up fighting soon enough when she got old enough to mingle with Mama's other cats. (She wanted to take in the whole cat world.) Discovering she was not the Only Cat didn't do anything for Puff's disposition. She hisses and swears loudly, sometimes even when you try to pet her, though she mingles purrs with her vocalism. Her long fur tends to mat, since she no longer grooms as she once did. But woe betide if you try to cut out a clump!
I think Puff is spending her senior years happily. We're down to six cats in the household now, and she can lie down undisturbed just about anywhere she wants to. She's also the best eater I've got, accounting for a can of cat food every day. I was lucky she jumped up on the bed and sat still for her picture.