My dads JRT has a bit of grey around her mouth, but not really noticeable unless you're up close. She's almost 6.
Jackson will be 5 this year and has none. He looks basically exactly the same as he did at 1. lol. His coloring has changed a lot though, being a Yorkie and all. But sometimes his body color still changes a bit after each groom. He definitely lightens up in the summer, and then sometimes when he's shaved down, his back is really dark. Crazy.
When I let it grow out a bit, it's very silver.
When it gets shaved, it can either look like this
or be pretty dark: