By Erin Lukas
If you have friends with dyed blonde hair, you've probably heard them talking about how purple shampoo keeps their color from turning brassy.
But fading and brassiness isn't a struggle that's exclusive to blondes. Brunettes that color treat their hair can also develop unwanted warm tones — which is where blue shampoo comes in.
The easiest way to understand how both purple and blue shampoos work is to compare it to the color wheel theory. Similar to how purple shampoo neutralizes yellow tones in blonde hair, blue shampoo deposits blue-violet pigments into dyed brown hair.
"Blue shampoo works by canceling the orange/reddish undertones (the same tones that are commonly called brassy) that are part of the underlying pigments," explains Mincho Pacheco, master hairstylist and colorist at James Joseph Salon. "It neutralizes the orange by making it more deep."
Brunettes who color their hair will benefit the most from using blue shampoo because the pigment absorbs better into hair with expanded cuticles. (Your hair cuticles expand when you dye it.) For virgin brown hair, these shampoos will make your color extra shiny, because most of the pigments will stay on the surface of your hair.
The stylist recommends that unnatural brunettes use blue shampoo once to twice a week, while natural brunettes can wash with it up to three times a week.
Ahead, we've rounded up the best blue shampoos for brown hair.
dpHUE Cool Brunette Shampoo
On top of reducing orange and red undertones from brunette hair, dpHUE's blue-toning shampoo also contains silk proteins, which prevents breakage and leaves hair super silky and smooth.