Nº.4P repairs, cleanses, and tones with patented OLAPLEX technology for all blondes, lightened, and grey hair. While hydrating, Nº.4P neutralizes brassiness and brightens the blonde. The highly concentrated pigment allows customizable toning levels ideal for medium to light blonde tones (levels 7 and up) in which yellow or brassy tones need to be controlled. Compared to top purple shampoos, users found their hair 3x brighter using OLAPLEX Nº.4P. The longer you treat, the brighter the toning results, but we recommend starting with one minute and going from there.