Purple Shampoo

I was just wondering if anyone's tried purple shampoo that hasn't dyed their hair blonde or have blonde hair naturally.

Would pigment even be deposited in black hair?

I was thinking maybe it would tone down the brown and give my hair a cooler shade under the sun instead of brown/red.

Purple shampoos are used for neutralizing yellow tones; it probably would not make a significant difference if your hair was very dark...

It will do nothing. I have blonde hair (at the top of my hair) and my sides are grown out shaved sides (virgin hair). Whenever I feel like using purple shampoo, I'll just apply it too all my hair cause it's a hassle to apply it on certain parts. It won't make a difference to your hair, and if it did, it wouldn't be noticeable. (My virgin hair is a dark brown / black, like most Asians).