When new, there was a very large palette of colors for both interior and exterior. That was then...
Even 20 years ago upon restoration of my car, it was clear that the available color palette from any/all sources wasn't as comprehensive as when new...which is why I chose black. There will always be black available.
That being said, AlexD one of our board members had a similar challenge with carpet. He went to extraordinary, even heroic lengths to get turquoise carpet made to match his original It was written up in a PW some time ago.
You may need to have custom leather dyed to match, and then seat covers custom made. It's not going to be cheap, easy or quick.
Thankfully, there is a fairly well known upholstery shop in your backyard: Heritage Upholstery. If you are serious about your project, a visit to Tony Hazell would be worth your while. They are in Palm Springs.
If you are totally dedicated to absolute perfection in color match, there's a guy in the Netherlands, probably the world's expert. Henk van Lith, at HVL Exclusive Italian Interiors...but he can offer some insight. info@carinteriors.nl.
www.hvlclassleathers.com. His specialty is Italian, but I'm sure he can help you. Good luck!