Wella dark brown violet

[rachielee1]

I have a friend that has been box coloring her hair jet black for years, she would like to stay as dark as possible but now add a very small tint of violet. I would like to stay away from bleach if at all possible. Is the only way to do this to do a soak cap and apply color after? Also would you be able to see the violet at all with a level 2 or should I do a level 3? Thanks for the help!