First was a fail but then
The first time I used it, I left it in for 10 mins and it did not cover my grays at all. Then I thought I'd leave it longer. I put it in and was busy with something and it was left in for about 30 mins and it worked. I have resistant grays and box dye does not work on my hair so I usually buy from a store that has for resistant hair. I am really happy with how easy it is to apply and that I got it to work. The order was sent quickly.