This is a really great product, it does get rid of unwanted yellow tones, which is what the product is for. This is perhaps the strongest purple shampoo I've used to date.
I usually leave purple shampoos in for 5 minutes or longer and it gives me the results I want. With this shampoo it's recommended not to leave in for long as the shampoo is quite strong. It has turned my whiteish parts purpleish. Though it does look good, it was not the result I wished to achieve.
Overall, a very good shampoo for getting rid of yellow tones.
This product was the most reliable out of the various products i used to get the orange pigments out of my hair when going blonde. It's quite strong so you only need to leave it in your hair for a short amount of time and you should be fine. It smells great and leaves your hair feeling good :)
Tips: Wash hands afterwards as there is a purple stain to your hands if left on your hands for too long. Or use gloves.