I had someone order a cake with a vanilla pudding filling. I will be making the filling with vanilla pudding and heavy whipping cream. I am assuming that this needs refrigeration. My question is, the cake will be covered in BC with fondant accents, will the fondant coloring run onto the BC if I put it in the fridge? I will be using white BC with black and red fondant.

I've done lots of cakes with buttercream and fondant accents, and I've never had any of the colors run. I moisten the back of the fondant a bit before I put it onto the BC, and you do need to be careful not to make it too wet or that will make the color run. I wrap my cakes in plastic wrap and put them in the fridge and they're fine.