I used it only once or twice, this week.
On Tuesday night, I decided to use shampoo to wash my hair, because that is what the instructions call for. Up until this point, I did not do that, because I forgot, and because I did not have any bottles of shampoo left. I completely forgot about the samples that I have. On Wednesday morning, I applied a bunch. I did not see a lot of colour, but I felt that it did darken the hair enough to reduce any white shine.
I will keep on going, because I want to make sure that I used the product properly, before I pass judgement.