How does this tinted shampoo differ from a permanent hair dye?

Unlike permanent oxidation dyes, which open the hair cuticle and alter melanin inside the cortex, this Victoria Beauty Keratin Therapy tinted shampoo works by laying colour pigments onto the outer layer of the hair shaft. The formula contains no ammonia and no oxidising agents, so it cannot lighten hair or create a permanent shade change. Instead, it provides a gentle colour refresh that gradually washes out over several shampoos. The added keratin is a cosmetic protein that coats the hair surface, helping it feel smoother and look more light‑reflective, which can make the deposited colour appear more even. Because the pigments only coat the exterior, the result is softer and less uniform than a salon dye, and it fades evenly with each wash. This makes the product suitable for maintaining or enhancing an existing light brown tone between colour appointments, but it will not cover grey completely or shift the base colour dramatically.