I used it a few times before and each time it worked really well. Of course, if your hair is super dark (near black) it will lighten a bit and really show it's true colors in the light, but the times I used it (both when my hair was dark dark brown and when my hair was a lightened brown) I was impressed with how well it showed up. Of course, with any permanent hair color job, you've gotta up your moisture and protein. But just speaking of the Hi Rez's performance and not how your hair may particularly react to it, it works very very well. My hair was fine afterwards but everyone's hair is different.