I have medium brown hair with cool (rather than warm) tones. I tried this product in endless ways - before washing my hair, after, on wet hair, on dry hair, leaving it in for the directed time (10-15 minutes), leaving it in for extra time (45+ minutes), using my hands to apply, using a brush to apply, etc...and the color is barely noticeable. I don't even have dark hair, which can still use this product according to their claims. Rubbish. A lot of money for something that doesn't actually change your hair color. When I reported this issue to customer service THREE TIMES, I continued to be ignored, or get one response (to only one of my claims) and then get ignored thereafter - even when I sent two additional emails to confirm they'd received my response. What a joke of a company.