IMHO, I would get the color code for the exterior paint and see if they can match it. But, I am certain there are some guys here who have done this mod without color code matching and it looks just as good.
The color code for your Artic silver can be found in this link:
http://www.renntech.org/forums/index.php?autocom=content&code=colors_boxster
You might have to register / sign in to view it.
BTW, their legend states: BOLD is for "conventional paints" and Normal Text is for "water-based paints".
Good luck with that! Let us know how it goes!