What type of hair color products are mixed with a developer?

Permanent hair color products are mixed with a developer to activate the color and facilitate the oxidation process that allows the color to penetrate the hair shaft. The developer, which contains peroxide, works by opening the hair cuticle and allowing the color molecules to enter the hair. This process not only deposits color but also helps to lighten the hair if needed.

In contrast, temporary hair color does not require a developer and simply coats the hair without altering its structure. Direct dye products also do not need a developer because they rely on a non-oxidative process to impart color on the hair. Highlighting kits may vary, but they typically contain lighteners and are not specifically categorized as permanent color mixed with a developer for all-over color. Therefore, the answer accurately represents the type of hair color product that must be mixed with a developer for effective and long-lasting results.