Darkening hair highlights is a process of reducing the lightness of previously highlighted hair, bringing it closer to the natural hair color. This technique is often used to correct overly light highlights, blend them with the natural hair, or simply achieve a different look.
There are several methods for darkening hair highlights, including using a toner, a semi-permanent hair color, or a permanent hair color. The best method will depend on the desired level of darkness and the condition of the hair.