I did that to myself over the weekend! I used a different name brand haircolor and it came out patent leather black!
I bought a hair color removal kit - did it - then used my regular hair color. It's still a little dark - but I'm getting used to it now.
I used a hot oil treatment after all that to help my hair not look so dry.
__________________ Kim , Rebel ,and baby Dixie 
RIP my sweet Lucy |