The most correct way to accomplish assembly line correct appearance is to use the backs of the colored plastic parts to match against, this has been found to most correctly replicate the original appearance.
In all likely hood there will be more than one shade and or color, the colored interiors were notorious for their mismatch, however survivors and cars restored using NOS parts don't match perfectly so many have come around to the realization that the cars were not "perfect". Personally I like the calculated degree to which things were allowed to pass based on the volumes being produced.