Redwood Foods versions of these are sold in Holland and Barrett, Asda and wholefoods shops. Gravy granules. Just because you're feeding a vegetarian or vegan doesn't mean they have to have 'vegetarian' gravy (you know, the thin watery stuff that looks like a dissolved vegetable stock cube).
If your tongue is stained black or dark brown it may be caused by medications and certain foods/drinks. Drinking several cups of coffee or tea per day may stain the tongue; some people who supplement with green drinks containing chlorophyll may notice a very green tongue.
Picture from Wikimedia Commons. In some people there may be a brown to black discoloration of the tongue which occurs in patches or streaks. This may be present from birth and is usually not a cause for concern provided that it does not enlarge over time or present with other symptoms.