My hair was already dyed blue/grey with Manic Panic Blue Steel. Keracolor has boosted the colour on the first use. I did use it on dry hair first time and left it on for 20 minutes. The bottle recommends 3-5 minutes on wet hair. I will do this for maintenance. Product smells lovely and left my hair very soft. I am in a chlorinated pool daily and need something to stop yellowing and fading from pool water.