Which type of hair color is primarily used to blend gray hair?

Semi-permanent hair color is primarily used to blend gray hair because it allows for a more natural look by depositing color without lifting the existing pigment. This type of color typically lasts through several shampoos and gradually fades, which is ideal for individuals who want to soften their gray without committing to a more permanent solution.

The formulation of semi-permanent color is designed to penetrate the hair shaft slightly but not alter the hair structure as permanent colors do. This makes it suitable for blending gray because it can harmonize the natural hair color with the grays while allowing for an easy transition as the hair grows out.

In contrast, permanent hair colors would provide a longer-lasting result and can fully cover gray hair, but they involve a chemical process that changes the hair structure, which may not appeal to everyone seeking a subtler approach. Temporary colors provide very short-lived results, generally washing out after a single shampoo and not effectively blending gray hair. Lighteners, on the other hand, are used primarily to lighten hair rather than cover or blend gray hair, making them unsuitable for this purpose.