Each of the factory vinyls and fabrics have their own part number. The larger trim shops had those catalogs, back when the cars were new. They used to have shelves of those catalogs, year by year. Using those part numbers to order fabrics, just as you'd use a factory part number to get a piece of molding for the car's body.
Fabrics and vinyls DO fade with time, but automotive fabrics and such usually fade at a slower rate than residential fabrics seem to do. The factory trim codes, up until the '74 model year in C-bodies (and probably other Chrysler Corp vehicles) had a pearl/metallic tint on top of the base color. As this top coat ages, it can look dirty, but no vinyl cleaner will make it look "clean" again. Just part of the deal, as I determined on my '67 Newport with the Pearl White vinyl interior. As mentioned, a piece of material from under a seat, where the "sun don't shine", would be the best way to determine the original color of the material, rather than in a sun-affected area.
In doing a "clean-up" on an interior, I believe that a cleaner you mix yourself, then administer with a soft brush or sudsy sponge, is best. A former member of one car club I'm in had great results using Simple Green on a '66 Buick Electra. We were surprised how well it turned out.
When using any soap/cleaner, be SURE to get the dirty solution off of the material as soon as you can, consistent with good cleaning. Then rinse it with clean water until the rinse water comes out clean. After that dries, repeat if needed with the soap. Then do the final rinses. After that has dried, a protectant of your choice can be buffed on and off, even multiple coats spaced a week apart, might be considered.
This is one area where a little higher level of execution, with multiple cleanings, can be worth the additional effort.
One other consideration, in the area of material "color", is "dye lots" and the color variations between them. I learned of this when I worked for a drapery manufacturer. We'd have 6 partial bolts of a particular fabric in stock. Few of which exactly matched each other. When a customer came to have a damaged panel, I had to take a sample from the drapery and match it to what we had in stock, hopefully finding a close-match, if not an exact one. As automotive fabric colors are usually held to a much higher standard of performance/durability than residential materials seem to be, this should not be nearly as great of an issue, I hope.
Keep us posted,
CBODY67
