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.
Discoloration of the tongue can be from many causes-often the color of a liquid or food. It is often caused by yeast also. When some one is on antibiotics the oral flora changes - bacteria is less, yeast increase; bacteria can also cause color changes. Some diseases, variants may cause changes.