1971 FY1 Question

Hi all, I have a 1971 Dodge Demon I have been working on, I'm just about ready to get it painted but I have a question, the original color on the tag is FY1, but I have seen so many different cars claim to be FY1 and they range anywhere from almost white to vibrant yellow, what causes these differences? And also, I'm looking to be more on the vibrant end of that, what would I request from my paint guy while staying with FY1? I have uploaded some pictures of the car currently so you all can see what the previous owner had it painted to, it's got it's share of scratches and imperfections.
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Under the hood was touched up with some rattle-can, it was rough down there but back on the fire wall is the original paint, which is a little dull.