How to make Monsters Sully Cupcakes inside. Remove small portion of vanilla or white cake batter, add purple food coloring place that batter in a decorating bag with a size 4 tip. Add Blue/Teal food coloring to rest of batter. Fill cups 1/4 of the way and squirt purple dots into teal batter. Add the rest of the batter to each cup and squirt a few more purple dots into the layer. Bake according to box directions! I used the same concept for the icing using a Wilton tip #233 to decorate.