Tea is an old method of dying to a golden brown. Coffee will work, too, but have a more brownish color. And, the tea or coffee do not have to be very hot. Just let them soak over night or for a few hours. If you have some extra bone, try it and see. Or, go to the butcher shop and get some cow bone, boil and clean it, then dye it to see how you like the result before you put in your good ones.