With an electric mixer, beat butter until smooth. Add confectioners’ sugar, milk, corn syrup and vanilla and beat until smooth. Divide frosting among 3 bowls and tint turquoise, green and pink with food coloring.
Smoothly spread each color of frosting onto 8 cupcakes. Transfer frostings to 3 resealable plastic bags and snip off a corner on each bag.
Pipe frosting in contrasting colors onto cupcakes for butterfly bodies. Insert candies into some of the frosting bodies. Make heads using mini Gobstoppers in a contrasting color. Insert a pretzel on either side of each body for wings. Cut 2-inch pieces of licorice and insert above heads to resemble antennae.