Tone-perfecting products to keep color as fresh as salon-dyed are more popular than ever (open in new tab): blondes have weekly gilding with violet masks, redheads add red gloss for extra warmth, warm chocolatey strands Those with strands have a blue formula to keep the hue from skewing orange in the weeks following the appointment. But raven-haired beauties and deep, dark, cool brunettes have been left without a color boost. Now comes an adult iteration of Nickelodeon Slime (opens in new tab): Matrix's Dark Envy, a new line of green-enhancing formulas.

The three-piece shampoo, conditioner, and mask set is the first of its kind and was created to drive unwanted warmth out of color-treated and virgin hair. So why not a blue shampoo that keeps cool brunettes cool and doesn't cut it?" the brand's renowned colorist, George Papanikolas, explains the simple theory behind it: "When you think about neutralizing shampoos, you need to look at the color wheel. Going to the opposite end of the spectrum neutralizes undesirable toners: blue shampoo neutralizes orange, green shampoo neutralizes red. Blue shampoo neutralizes orange, green shampoo neutralizes red. If you use blue shampoo to neutralize orange or purple shampoo to neutralize yellow, you will still have red in your hair."

That underlying redness makes your hair color look duller and less rich: high color shampoos that wash out your hair without fading, color-depositing masks that are perfect for weekly deep treatments, and conditioners that protect against overdoing color. It's.

If you're a warm brunette, stick with blue. But if you're shooting for a vampire vibe, simply want to enhance your natural tresses, or just want to know how you feel about getting slimmer (opens in new tab), grab some green.

For more stories like this, including celebrity news, beauty and fashion advice, savvy political commentary, and fascinating features, sign up for the Marie Claire newsletter.

Click here to register (opens in new tab)