PerHarper’s Bazaar, purple shampoo actually works with color theory.
The best way to get an even tone is touse the purple shampoo on wet hair.
Here's Why You Should Think Twice About Putting Purple Shampoo On Dry Hair
If you use purple shampoo to brighten your hair, experts advise to only do so with wet hair and to not use purple shampoo on dry hair due to patchy results.
