After coloring and rinsing hair, wait at least 24 hours before washing it with shampoo. Waiting 48 hours is even better, as this gives the color more time to set.
If the hair dye is red, washing only three times per week is best to avoid fading the brilliant color. When shampooing colored hair, use a shampoo and conditioner specially designed for color-treated hair. Look for hair products with sunscreen included to maintain the color's intensity. Also avoid washing hair for a day or two before coloring to protect it from the harsh chemicals of shampoo and get a more even coloring.