Style

How purple shampoo will help your hair color last longer

Need a break from red and blue? Let's come together to talk purple. Purple shampoo, that is — which, if you're someone who dyes their hair blond, could be the miracle product you've been waiting for.

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We may have discovered the secret to Gwen's beautiful-alien ways.

If you've ever tried to lighten your hair at home — or caught sight of your reflection halfway through a double-process treatment — you're familiar with the dull, one-dimensional yellow that remains after bleaching. It's not an especially natural or flattering shade, which is why a good colorist will then apply highlights, lowlights and toner. (Sidenote: This is also why your salon visit takes four hours and costs a small fortune.)

RELATED: 11 tips to help your hair color last longer

Unfortunately, dyed hair likes to slowly creep back toward that brassy yellow over time. That's where purple shampoo, which is kind of a "toner lite," comes in.

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In five minutes, your hair will be this color forever. Just kidding!!

The product goes on, you guessed it, purple — a bold, somewhat alarming violet that will stain your bathtub if it dries — but rinses out clear. For about five minutes in between, that pigment works to neutralize those brassy shades with its magical, opposite-end-of-the-color-wheel powers, explains hairstylist Susan Monahan of Warren Tricomi salon.

And get this: It works. While an over-the-counter product can't replicate the nuanced work of a skilled colorist, it can help keep that blond shade bright for months, helping you stretch out the time between salon visits.

RELATED: 5 pro-quality hair dyes that let you skip the salon

"It's great for cutting the brassiness in blond hair, especially in city areas where there tend to be a lot of mineral and rust build-up in water," celebrity colorist Ryan Pearl of Cutler Soho salon tells TODAY.

It can also help neutralize yellows or gold to make blond shades appear brighter, adds Victoria Hunter of Whittmore House Salon.

But it's not just for blondes. It can also be used to touch-up highlights, keep trendy pastels looking crisp, or give grays (natural or otherwise) those chic blue undertones.

So, what's the catch? Well, there is the aforementioned tub-staining, so be sure to clean up quickly.

Plus, "covering an entire head of hair in the shower with a stain is tricky," Monahan explains to TODAY. "Most people don't add enough shampoo to really coat every hair."

And it is possible to go overboard. Pearl recommends using it just once a week maximum.

RELATED: Lowlights or highlights? A stylist explains hair-coloring techniques

With that, here as some purple shampoos to try. Let us know how it goes!

Matrix Total Results So Silver Shampoo, $12, ULTA

ULTA

BLNDN Brighten You Brightening Shampoo, $20, Amazon

Folica

Redken Blonde Idol Sulfate-Free Shampoo, $24, Amazon

Amazon

Alchemic Shampoo Silver, $25, Amazon

Davines

You can also try a purple conditioner for a similar effect, suggests Monahan. Here's her go-to:

Alchemic Conditioner Silver, $30, Amazon

Davines
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