Step 3
In a large bowl using a hand mixer or the bowl of a stand mixer using the paddle attachment, beat butter until fluffy. Add powdered sugar and beat until combined, then add vanilla, heavy cream, and salt and beat until combined. Divide mixture into 4 bowls: 1/3 of the frosting in one (dye green), 1/3 frosting in another (dye red), and the rest divided evenly between the other two bowls (black and white). Place into 4 separate piping bags.