Toluene-2,5-Diamine Sulfate permanently colors hair via oxidative reaction. Permanent dyes need to be mixed with peroxide just before application on hair. Oxidative Dyes can be primaries or couplers. Primaries are usually substituted p-Diaminobenzenes or p-Aminophenols. They are colorless and react with the oxidative couplers in the presence of Hydrogen Peroxide which results in the desired hair color. The exact color obtained depends on the other ingredients that are added to the hair coloring product.