The only difference is, where purple shampoo is intended to be used by blondes, blue shampoo is better suited to brassy brunettes. "In the same way that blonde hair can turn brassy, brunette hair is also prone to oxidizing which can bring out orange or red tones," brand ambassador for Charles Worthington, Ken O' Rourke, explained to YOU Magazine. Sign us up. "Hair tends to be affected by the elements, which is why a weekly use of the blue/purple and silver shampoo keeps the hair vibrant, brass-free and not dull," celebrity hair stylist Kieron Lavine told Huffington Post. Not only does regular use of blue shampoo promise to keep your hair color looking fresh and free from brassiness, it also promises to add shine. If you spend a lot of time in the sun, shampoo every day, or blow dry your hair frequently, your color is likely to fade faster, causing brassiness to appear. Speaking to Huffington Post, Burnett added, "Shampoos definitely help avoid brassiness but this is also so dependent on the individual's styling routine." Not only does regular use of blue shampoo promise to keep your hair color looking fresh and free from brassiness, it also promises to add shine. "Hair tends to be affected by the elements, which is why a weekly use of the blue/purple and silver shampoo keeps the hair vibrant, brass-free and not dull," celebrity hair stylist Kieron Lavine told Huffington Post . You may have heard of purple shampoo, or walked past it on the shelves at your local drugstore, but have you heard of blue shampoo? Sam Burnett, owner and creative director of Hare & Bone, agrees. Simply speaking, blue shampoo is shampoo with a blue tint. Who Needs Blue Shampoo? Both O'Rourke and Lavine recommend using blue shampoo no more than once a week, hinting that there is such a thing as too much of a good thing as they have been known to strip hair of moisture. According to cosmetics giant L'Oréal Paris, the new formula is said to be a godsend for brunette color-treated hair, working in a very similar way to purple shampoo. Just like purple shampoo, blue shampoo is formulated to bust brassiness in color-treated hair . Blue is the opposite of orange, so a blue shampoo will cut through the brassiness in lightened brunette hair and restore it to a cool or neutral tone. While the best way to avoid brassiness is to ensure that your hair colorist applies the hair dye correctly, blue-based shampoo can assist in maintaining the health of your hair, removing unwanted tones, neutralizing color, and keeping it looking cool in-between appointments.