GM used to let you put just about any color in any car. They had combinations that were "not recommended" but if you nagged them enough, you could get an oddball.
The green interior you speak of, sounds like it's just old and the color has changed.
The Limelight Green was available in 69 with Gold, Green, Parchment and Black interior.
You won't find the interior color code in the VIN. You will need to look on the body tag on the cowl. If your car came with a green interior, then the code on the tag should be 256. Check out
Pontiac GTO - The Ultimate Pontiac GTO Picture Site or
GTO Alley! to find lots of info on decoding your car.
Hope this helps!
mac
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