I read that you can add violet color to the chocolate BC, and that you don't need a lot. Try a small sample to see how it works. I haven't done this yet, but I read about it on this site. Also, add meringue powder to prevent bleeding if black will be on another color (such as writing black on white BC).
I have told students that in order to get black and you don't have any is to use blue, red, yellow. adding one color at a time till you get it. My son called me one night and the stores were closed and he needed black. I told him the same and he was able to achieve black with those three colors. He did a Dora cake and needed alot for her hair. HTH>
Quote by @%username% on %date%
%body%