I haven't used tea or coffee on wood but it should give a little more shading to it. Another thing you can do is ebonize it with vinegar and iron. Dissolve one of those big 0000 steel wool pads in a quart of white vinegar for a few days until the pad is all dissolved. Leave the lid loose since the process will build up pressure. That will make anything from a light grey to almost black depending on the wood. I tried it on the swamp ash I have for my Telerauder and it gave a medium grey tint. Not to my liking but you may get a different result. Try it on a scrap and see if you like it. If you don't have a scrap, let me know and I'll do one and post a picture of it here. It won't be roasted, though. Roasted will be much darker. You could take a Q-tip and put a dot inside one of the cavities to see what it does.