decorating icing

How Do You Color Frosting Blue? How to Make Blue Frosting. To make light blue frosting, mix 1⁄2 container of vanilla frosting with 1/8 teaspoon of blue gel. To make medium blue frosting, mix 1⁄2 container of vanilla frosting with 1⁄4 teaspoon of blue gel. To make blue frosting, mix 1⁄2 container of vanilla frosting