1. Coffee Coffee works great if you’re looking to go darker, cover gray hairs, or add dimension to dark tresses. Simply brew a strong coffee (espresso works well), let it cool, and then mix one cup with a couple cups of leave-in conditioner and 2 tablespoons of coffee grounds. Apply on clean hair and allow to sit for about an hour. If you use apple cider vinegar to rinse, it will help the color last longer. You may need to repeat the process a couple times to see noticeable results.