Freshly dyed hair can be washed after 24 hours. It takes this long for the new color to be fully absorbed into the hair shafts.
Freshly dyed hair responds well to shampoos and conditioners specifically designed for color-treated hair. Avoid shampoos and other hair care products specially formulated to treat dandruff or to clarify the hair. These types of products are very harsh and may strip the hair of its new color very quickly. While gentle shampoos help preserve new hair color, the color eventually gets stripped away after enough washings. Spreading out washing intervals helps preserve freshly dyed hair color longer.