Gray hair - good question. Barefoot has some herbals that are supposed to get rid of the gray. Top Knot I think it's called. I've been using it for a couple of months now and haven't seen much improvement.
But it's a good question. I don't know the exact physiology of how it works but I know high stress gets you gray very fast. I think it has something to do with testosterone conversion getting interupted somehow. Or it could be calcuim metabolism. I just don't know.
Don't use the stuff from the pharmacy or grocery store. It has lead in it. Don't need lead poisoning.