The Dwarf Fortress Wiki, while a wonderful help for most of the time, still falls short from time to time, especially in some of the minor articles.
Something I was unable to find conclusive data about was the uniqueness of the various stone / ore / bar colors.
Simply put -- Which stones / alloys / bars / wood (any construction eligible material) provide which color when used as a building material?
It's easy when you're building something small and can use entirely one type of rock, but when you're in the middle of a megaproject and you're aiming for consistency, you don't want to be looking at the item screen wondering whether the batch of newly excavated "Slate" matches the "mica" you've been using up until that point., and it would be nice to have a list to be able to compare to at a glance.
Note: According to this, there should be 16 different categories.