I voted Charcoal for your car because I agree with what others have said about the red sticking out like a sore thumb. It would be way too bright for what the interior has going on already.
On my car, being blue, i think body color would fit in quite well and not stick out being that it is a much more subdued color to begin with.

You could always try painting it in carbon fiber style. I have seen patterns that are used to create the effect at local paint shops. If you like the look, but didnt like the fit of the film it may be an option for you.