Robin H., thanks for all the info. I wonder if it was mixing the type colors, or simply a lot of added color, or a lot of extra mixing, or a combination of all. The different color on the top layer is very interesting. Was it the same for the ones that dried well and the ones that were still wet? It is also interesting that it was an icing gone wrong with black in it again.
I know deeper colors like red and black darken quite a bit if you let them sit for a day or two, but that sounds excessively dark. Chef Allen over at Global Sugar Art recently put out a video introducing his new line of colors, and specifically shows how both red and black darken. He says most colors will develop when it oxidizes/is exposed to air. I wonder if this means the top of the icing will darken more, as it is exposed to more air, or if the fact that the outside dries first would stop that action. As far as I know, the darkening stops when the icing dries, but not sure.
If you try repoducing it, I would love to hear how it goes. I mostly have gel colors because almost all my Wiltons leaked everywhere, so I tossed them. If they came in a tube or bottle similar to Americolor gels, I would still use them because I love the intensity, and mix my colors by eye anyway. Chef Allen claims his black was specifically formulated for his line, and is the best out there. Wonder if anyone has tried it?