horns get stained from the blood in the velvet,if a deer starts rubbing the velvet off before his horns are totally hard set & there is still blood in the velvet it will stain them,from what i have seen hunting around different places in Tn the it can be just a local trait to rub early,5 miles away you may never see a chocolate colored rack,it defintly helps them to grow bigger when the white horns don't make them as easy to see,i have yet to get a dark set but maybe someday it will happen,mike300wm