The color you are using is a temporary color. A permanent haircolor will behave differently, since it is working by another chemical method. The color molecules actually enter the hairshaft to become permanent. this is achieved with a small amount of ammonia and peroxide. If this is still something you would be interested in you might want to try EcoColors dark brown. When applying the color you can dilute the developer by half with water to achieve a deposit only haircolor.If you have gray hair you should apply the full strength color mixture to your gray roots and then dilute the color mixture to apply to your previously colored hair. You can do the patch test and the strand test to make sure this is the color that you want but Since you have a previous color from another brand on your hair Ecocolors cannot guarantee desirable results.