Olaplex No. 4P Blonde Enhancer Toning Shampoo is a highly concentrated purple shampoo designed to cleanse, tone, and repair blonde, lightened, and grey hair. While traditional purple shampoos are notorious for leaving hair feeling dry, straw-like, and brittle, No. 4P is formulated with Olaplex's signature bond-building technology to hydrate and strengthen while neutralizing unwanted warm, brassy tones.