Had to laugh when I read "walnuts" and "colorfast" in the same post!! I harvested a ton of walnuts last year in one of our state parks, and, after proper drying, husked them (or what ever you call it!!). My hands, even through gloves, instantly turned a deep brown. The color lasted for MONTHS!!! Maybe that's why the "earlier" ladies used the walnut coloring for hair dye?