Welcome, David.
It will be great to see another Minx going. I’m always thrilled to hear of the more rare Rootes. The Minx does have a great look doesn’t it!
The Rootes color codes are documented here: https://www.teae.org/cars/paint-color-codes/
The Berger codes are a more modern equivalent. It is a starting point for cross-reference. Berger doesn’t have automotive paints on their website any longer, but at one time they were somewhat of a standard for cross reference. I wish I had the whole list in Munsel numbers…
Here’s a scanned picture of some paint chips for reference.
http://vintagebritishcables.com/Hillman-Humber-Singer-Sunbeam-Paint-Chips.php
Best Regards,