I had to make gumpaste in black, I looked everywhere for how, I figure this out on my own, take cocoa and mix it in your gumpaste and then add Black gel coloring and a tinge of purple, it made lovely black
Bonnie

That combination should make a wonderful black. There should be posting somewhere on making RI, fondant and butter cream black, we've all had the same stuggle. Hope your gum paste is a perfect black.