If you do a google image search for "HK416A5" you can see really good examples of RAL 8000 as applied to firearms and compared to existing FDE shades. The mustard-y yellow color of the stock, grip, dust cover, etc, is the color you're looking for, while the receivers are pretty close to Daniel Defense FDE. There are some images of it equipped with the FDE ACOG and PEQ-15, like this:
In the last pics you can see it has a green-brown effect depending on the lighting. The US uses a similar but darker (and better looking, IMO) color called Federal Field Drab 30118. It's also known as Marine Coyote Brown, LMT/B5 FDE, SOCOM Dark Earth, and KAC Taupe. It's the same "FDE" FNH uses on their FDE frames for the FNX-45. It also comes in a very durable rattle can form by Aervoe, called Field Drab. The following images all feature the same color, Field Drab 30118:
Both RAL 8000 and Federal Field Drab 30118 are classified as "green-brown" colors. Between the two, RAL-8000 is much lighter, while both colors maintain a transitional property whereby they can both appear brown or green/greenish in different lighting. Field Drab is very dynamic in that respect, and is one of my favorite earth tone shades used in the industry. I wish it was offered as a gear color across the major manufacturers and retained that transitional characteristic.