I was so excited to try out this product! It said on the box that it works on "dark brown" hair, but it unfortunately doesn't at all! I put this on and left it in as long as it said, but what it left me with is a strange charcoal grey colour in my hair rather than teal. This wasn't a cheap product either. I'm so disappointed, especially since the girl on the box looked like she had very dark hair, and the pictures on the back seemed to match my hair colour. I should have known it was too good to be true! Buy bleach and buy punky colours or wella. Don't buy this product unless you're blonde or close to it.