Green (unripe) walnuts have a thick outer husk (for want of a better word) that you have to remove to get to the nut itself. If you handle them much they will turn your hands a nice brown color. When the nut ripens the “husk” turns black. The husk is where the dye comes from. The hulls (shells) wouldn’t have much if any color
After family reunions when we were kids our hands would be brown for a week or so from the walnut wars we had with the cousins
After family reunions when we were kids our hands would be brown for a week or so from the walnut wars we had with the cousins