Which of the following is a characteristic of permanent hair color?

Permanent hair color is characterized by its ability to penetrate the hair shaft and alter the natural pigment of the hair, which allows it to lighten hair effectively. This transformation occurs through a chemical process that involves a developer (usually hydrogen peroxide) that activates the hair dye. The combination of the dye and the developer opens the hair cuticle, enabling the new color to be embedded within the hair structure.

This property of being able to lighten hair sets permanent color apart from other types of hair color, such as semi-permanent or temporary dyes, which typically only deposit color without the ability to lift or lighten the existing shade. Therefore, understanding that permanent hair color can lighten hair is essential for stylists when selecting the appropriate products for their clients.