I agree with TC.
There are a wide range of silvers and greys which compliment tans and browns, but I think I'd probably go with what looks good in terms of clothing for the percentage.
If you're wearing a dark grey suit, would you wear a tan shirt and a charcoal tie? I would.
If your suit is green, would you wear a red shirt and a charcoal tie? Probably not. In fact, you'd have to feel really darned secure to wear a green suit at all.
If your car is the dominant color, the roof ought to match it.
Point is, color samples in the right proportion tend to line up in schemes that either do or do not make sense. I'll cook something up for you and post it with this thread ... We'll see if this works the same for you as it did for me. I did my new blue and orange scheme by committee here on the site.