Permanent dyes create a drastic difference and last the longest. All hair colors will eventually fade or change over time but permanent dyes last an incredibly long time and do not wash out over time. Permanent dyes typically only require root touch-ups ever few weeks or so.
Generally, when people are seeking permanent hair coloring results they use oxidation dyes. Oxidation dyes typically contain diaminotoluene, a coupling agent, and an oxidant. The ingredient that is typically used for oxidation is hydrogen peroxide and ammonia is typically used as an alkaline. Hydrogen peroxide lightens the hair so that is is more receptive to accepting hair color. Ammonia essentially creates holes in the hair shaft to allow the dye to lock onto the hair. Ammonia also helps speed up the process of dying your hair.
