I bought #3 ash gray. While the instructions say to leave it on for 30 minutes minimum, I would say that with the amount you need to put on to make removal easier, the product will not be dry in 30 minutes. Plus, if you want better color pay-off and longevity, it would be best to go for 2 hours or even overnight. Ash gray was not as dark or gray (which was expected for a Korean eyebrow product), and it looked more dark brown than anything.