To counter red tones, be sure that you do not run full strength color though the ends with every application. Always apply color full strength only at the roots and then dilute the remaining color mixture by half with water to apply to previously colored ends. Try using dark ash brown or even Ecocolors black DILUTED on your ends. Red tones in the hair may also be caused by iron in your water or well water. Alkaline shampoos may also lighten your ends. Try a shampoo free of lauryl sulfates and castille.
