Combine the butter and shortening together in a bowl of an electric mixer, using a paddle attachment, beat on medium speed until smooth, about 2 minutes.

Add half of the powdered sugar and continue beating on low speed for additional 2 minutes, or until the mixture is creamy, scraping the sides of the bowl with a rubber spatula as needed. Add the remaining powdered sugar, vanilla, and milk, and beat until the frosting is creamy and fluffy, about 2 minutes more. Add any food coloring desired at this time, and beat on low until light and fluffy.

Use immediately or store in air-tight container for up to 30 days.