If your hair takes color well, do a strand test on dry hair. If you rinse it out and end up with unwanted blue tones, you may be better off applying the shampoo to wet hair in the future.
Don’t leave it on too long: I accidentally left it on my dry hair for 30 minutes. My hair felt quite frizzy afterward, and even the Joico K-Pak wasn’t enough to get it back to normal.