Beat butter in large bowl with electric mixer on medium speed until light and fluffy. Add vanilla; mix well. Gradually beat in confectioners' sugar, beating until well blended after each addition, frequently scraping sides and bottom of bowl. Add milk; beat until light and fluffy.
Divide frosting evenly into 2 separate bowls. Stir in food color from tips below to tint each bowl of frosting desired color. If frosting is too thick to spread after adding color, gradually stir in additional milk.
Fill pastry bag fitted with a star tip with prepared tinted frosting. Pipe frosting onto cupcakes, as desired.
To create frosting twists, place 2 to 3 colors of frosting side by side in same pastry bag. Pipe frosting swirls onto cupcakes, as desired.
• Orange Frosting: 48 drops Yellow + 50 drops Red
• Blue Frosting: 100 drops Neon Blue
• Red Frosting: 150 drops Red + 10 drops Yellow + 3 drops Black
• Purple Frosting: 150 drops Neon Purple + 30 drops Neon Blue
• Green Frosting: 150 drops Green + 6 drops Black
• Gold Frosting: 100 drops Yellow + 1 drop Black