I think if you say what you said here, as Mom2kCk below says - they'll get what you mean.
Here's what mine does. I have a bit more grey than you do - I'm naturally light brown. Because I don't want to color my whole head and I'm ok with grey, my stylist just uses foils targeted towards the top of my head where the greys are most noticeable. So in each foil I've got grey and some light brown. She puts in a lighter caramel color and so the greys turn lighter caramel - more like a highlight - and my regular hair looks a tiny bit brighter. So overall I look like I have highlights because the grey looks like caramel highlights.
She doesn't get all of my grey, but I'm ok with that. The overall effect is little bit of grey, caramel highlights and light brown hair.
So I am guessing they would do something like that for you. Hope that made sense :)