I sympathise with your dilemma. After all, the exterior/interior colors are probably the most personal decisions one will make when purchasing a car. This decision is difficult enough without the manufacturer limiting which colors are available on which lines! When I ordered my GT, I had determined I wanted the Coral Red Interior because I wanted something that made a statement. I also knew I wanted the M-Sport Line because I liked the look and the sport seats. With those decisions out of the way, it was now a matter of choosing the exterior color.
Unfortunately, some of the colors I was interested in, Kalahari Beige, Sparkling Brown and Mineral White, were not available with the M-Sport Line. Although I liked the Mineral Grey, available on the M-Sport, i felt it was too close to a color I had had on a Volvo. So you can see. Back and forth, forth and back it goes, trying to decide on a color! Sometimes I think we forget that the purchase is only for a few years, not for life!
But, nonetheless, we want something that says a little something about ourselves. Who we are, so to speak.
In the end I went with the Glacier Silver with the Coral Red. It certainly wasn't a profound color combination, but it will do.