He is probably just a blue tabby (grey is called blue in the cat color dictionary). A smoke has a totally stark white undercoat, not just lighter at the roots but truly white. Your cat appears to just have the darker grey markings over a lighter grey coat which is exactly what a blue tabby looks like.
Can we get a picture of his head? And if you happen to have pictures of his earlier days (so at like 5/6/7 weeks orso) that'd be great too.
There is no such thing as a smoke tabby though. Smoke means non-tabby + silver. Smoke cats usually have ghost markings on their face which will be easily recognized, so that's why I ask for a picture of his face. Some extra pictures would be great too, just to be sure the color is surely black or blue.
In this case I have to agree with Red Top Rescue. He is not a smoke, neither a silver. He seems to be a gorgeous Blue Tabby. The long fur can really make the Tabby nearly invisible, but it's there. That's the reason some parts of the body seem lighter and some darker. My Silver Tabby has the same; it's like there is no pattern, but her face gives it away ^^ So does her kitten pictures.
Give your Cleto a big hug from me, I love blue colored cats a lot <3!