The RAL paint color system is a European system and, AFAIK, is not used in the United States. I suggest you do some Internet searching for those that have come before you and have solved this problem.
Larry
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.