Paul, my first IM "D" was Porsche 356 silver with a medium blue leather interior, OEM silver/gray square weave carpeting, and beige top; the interior is a "medium" blue leather with coupe type seats that have the 356 perforation pattern. The colors all go very well together and look pretty good with the chrome/gold trim and black tires.
However, the 356 silver has a gray cast, so I had my new IM 356 Speedster done in the VW "Saphir Silver", which is a lighter color with a faint bluish cast. Carpeting will be the same OEM silver/gray square weave; leather Speedster seats are navy blue with white piping; top and tonneaus are all navy blue.
Bottom line is pick a color combo that YOU like - authentic or otherwise. One nice combo is the original 356 dark green color with beige carpeting, top, seats, etc.