I think the (sort of) consensus on this is:
- tool bags for other models were made of relatively inexpensive canvas
- SLs got the tool bags made of scraps of soft tops and upholstery
- there was no matching, however, of your car getting the tool bag made of he same fabric or upholstery material as the car was equipped with; these came at random
Having said that, I believe that if a given material was rarely used, the tool bags of this color were also rare. This is unless e.g. Daimler ordered some material, the usage was low and there were plenty of leftovers that were consumed for tool bags.
These are all my thoughts based on quite a lot of reading of the forum.