You may tone down your hair by taking dark brown, and equal parts developer...then dilute this color mixture by half with water and apply to your hair. Process for 15 minutes.(then shampoo and condition as usual) Remember any time you are trying a new color brand or formulation it is recommended you do a strand test to make sure the end color is one you can live with before applying the color to your entire head. Also do a pach test ahead of time to make sure you are not allergic to the product.
