For years, purple shampoo has been the anti-brassiness poster child when it comes to minimizing those inevitable, unwanted warm tones that occur slowly but surely in lightened strands. (In case you're curious,

frequent washes, sun exposure, heat-styling, and the minerals and chemicals found in our water can be held responsible.) Alas, to keep lightened hair looking as fresh, cool, and un-yellow as possible, purple can save the day. Since purple shades are best at canceling out yellow tones, those violet-hued shampoos are typically more effective for people with blonde or gray strands, and—plot twist—blue-toned shampoos are actually the far more strategic choice if you have brown hair, be it a dye job or your au naturel hue. 

I'll be going into more detail below, but since blue naturally cancels out orange, which is typically the underlying pigment in brunette hair, it's a better option than purple if you're looking to really combat that orangey brassiness that starts sneaking in a few weeks post–color job. Good to know, right? In addition to explaining what exactly blue shampoo is and how exactly it differs from purple shampoo, I've also rounded up the 12 best blue shampoos on the market right now. (Trust me—as someone who has been highlighting and coloring my hair since elementary school, I know my way around the color-correcting space.) Keep scrolling! Everything you've ever wanted to know about blue shampoo is just below.