I was using SugarVeil mix to make a black spider web and wanted to pipe a message within the web. The SV behaved very nicely when white, before I colored some of it black with gel. The gel made it runnier, and the black SV spread too much to pipe the letters. They all ran together.
So, after I put the web on the cake tomorrow, which will be iced in white Sugarshack BC, I might pipe the message within the web with black BC. Will the black BC bleed onto the white?
you should be fine if it is crusted well. I personally would not put it in the fridge either because once you take it out, there may be condensation whick may cause it to bleed!