Looks like RAL is a a type of color matching system similar to PMS chips but mainly used for powder coating. Right?
And what vinyl film are you looking for? Do you want translucent backlit as well as opaque (in case you want to light up your sign?). Lots of flavors for that and I'm not sure you got 3M or Avery products in Belgium. The only way we can match vinyl colors is to pull a PMS chip and look in a vinyl swatch book for a match. And in vinyl, close is good. Custom costs $$$ and you have to buy a full lot.
(don't know what language it's in, but it works).
(may be something in here useful)
Try a google search on the vinyl... but unless you luck out and Avery has those two colors as actual PMS stock you will need to get a chart. Go to a sign shop with your chips. Call em first and tell em you're a student. They should help you out if they aren't up to their arse in busy.
Good luck on your project. Sounds like they are having you do the full, proper research for a Corporate Identity. I like that.
Welcome to the forum.