I send them a picture of my shoes saying I want a matching belt in dark brown museum. They didn't told me anything about different shades of brown but I didn't ask neither hoping they understood what I am looking for.
I found a picture of a person that has 3 museum belt from VASS:
credit: Diavolo on the french forum http://engrandepompe.forumpersos.com/
He just mentionned Plum, Brown and Gold.
On the photo the brown would satisfy my need except it appears a bit...