One thing Bob Tallman once told me is the paint would never match 100%, close, but no cigar. He told me he would get shipments of equipment, it would all be Oliver green, just not every piece the same exact shade. That stands to reason, formulas do change, as well as paint ingredients. One thing that can be done is to take a part that is the color you want to a paint center, most have color computers now days, and can make a match, but then application can affect the shade, we learned that in the body shop several years ago. Air pressure and spray gun settings can make a difference.
Take care!!
Andy