I will say the car my wife is driving (2SS) looks really nice with the grey. I'd like to see it with the grey acrylic panels instead of the base cloth, which is how the early CTF cars were built. I don't think it is a bad choice at all. But the all black interior in Number 3 (Cloth 1LT) also looks great also. I don't think you can make a wrong choice between either of those two.
The SS is only about a month old, so even if were to darken at all, it probably wouldn't this early. But as far as getting darker from getting dirty, they are pretty resistant to that. So far holding color fast.