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Like color-correcting concealer, but for your hair.

Every blonde knows the mere utterance of a certain word can set off a level five hair alarm like no other: brassy. (Just thinking it gives us the willies.) Ladies who color their hair to achieve beautiful blonde hues of butter, gold, and platinum are on constant lookout for that brassy tint that’ll make an unannounced entrance at any moment, ready to make an emergency call to the hair salon. In a nutshell, brassiness is the unwanted warm tone that shows up in colored hair, and it occurs when the hair's warm pigments begin to break through the chemically lightened hair.

Well, blondes aren’t the only ones that have to deal with this highlighting hindrance; brunettes with highlights have just as much to worry about, though their brassiness might sneak up in a slightly more under-the-radar manner. Just as we’re forever indebted to the purple shampoos that came to keep brass at bay for blondes, there’s a similar color-preserving product that all highlighted brunettes should be using: blue shampoo. Blue-tinted shampoo helps keep brassiness away from brunettes of all shades by fighting the warm tones with the opposing end of the color wheel. (Think: color-correcting concealer, but for your hair.) Purple works well for blondes because it cancels out yellow-orange brassy tints, while blue fights orange-red brassiness that brunettes see popping through.

Like regular shampoo, there are plenty of blue shampoos for brunettes to explore in order to find your perfect elixir. For the ultimate color preserving system, go with Joico Color Balance Blue Shampoo and Conditioner ($16 and $18, respectively; ulta.com). It neutralizes the brassy tones and preserves hair color for up to eight weeks. For color revival and silky locks, the Madison Reed Tune Up Color Reviving Shampoo and Conditioner ($26 each; sephora.com) works wonders with its blend of blue and green pigments, argan oil, and keratin. When it comes to styling, give your brunette locks a leg up with the Color Wow Brass Banned Mousse ($24; dermstore.com) that’ll keep your hair looking luscious and rich.

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Blue shampoo is a total game-changer for brunettes—a coup de grace for brass. Do yourself a solid, and help keep your tresses fresh and vibrant between hair appointments with help from one of these little blue potions.