It looks like the paint is very weathered and that will make matching it difficult. I would suggest you go online and do a search for PPG Automotive Paint and find a distributor near you. They should have the ability to scan your paint and make recommendations on color. You may also be able to visit one of your local Parts Stores like NAPA, Autozone, Orielly's, Advanced Auto, etc... and ask them about automotive paint. I'm no expert, but have had good results with Matrix, Nason, and PPG products.......
Don't take this to the bank, but it looks very much like Ocean Green which those closest I've found is the more modern GM Paint Code WE5765. You could get a pint ( my supplier did ) mixed up and test it.
In the Tech Tips on Stovebolt.com you can find a lot of information about original paint colors .
Hope this helps and good luck.
