Hair can be colored — or toned — after bleaching it according to Clairol. In fact, as long as hair is not seriously damaged, bleaching it to remove all color before applying a new color leads to better results.
When hair is bleached, it oxidizes the melanin molecules in the hair, and this removes the color. Hair also contains keratin, which means it has a yellow tint after bleaching it. It is important to do a strand test on the hair before bleaching it to determine how it will react to the bleach. After bleaching the hair, do another strand test to determine how the hair will react to the dye. These steps prevent potentially damaging mistakes.