The purple offsets unwanted yellow & brassy tones. Water opens the hair shaft, allowing the dye to penetrate & neutralize yellow hues. The magic of colors opposite on the color wheel! Perfect for blonde & gray hair to eliminate yellow and brassiness. Effective for pool hair too. Tangie sulfate-free purple shampoo bar is infused with purple violet dye. With just one or two uses a week, blonde & gray hair turns vibrant and shiny, no yellow!