We’ll begin with permanent. If permanent hair color is used on the hair, a chemical reaction will take place to alter the hair cuticle. Ammonia, when mixed with hydrogen peroxide, oxidizes and opens up the hair cuticle. This is where the chemical reaction takes place. The structure of the melanin (the color) and keratin (the texture) in your hair change, in order for the dyes to deposit.
Permanent hair color can darken hair or lighten non-color-treated hair, and it can change both the color and the tone of your hair. It’s also what is usually selected when covering gray hair, as it is the strongest type of color. Permanent color is as the name suggests: permanent. Therefore, it will leave a line of demarcation where your roots grow in. But, the richness of the color will fade over the course of 6 to 8 weeks, depending on how often you wash your hair.