Color Brightening Shampoo should be used by those with blonde or gray hair if they would like to eliminate the yellow or brassy undertones. The violet pigment contained in the shampoo cancels out the yellow tones or the brassy red tones. It leaves the hair with a truer color, whether it is naturally blonde or gray or is color-treated. It also offers a gentle clean that isn’t damaging to overly treated hair strands.