Preheat oven to 350 F. Line a 12 cup muffin pan with cupcake liners. In a large bowl, whisk together flour, sugar, salt, and baking powder. Add in eggs, milk, vegetable oil, and vanilla extract, whisk until smooth.
Evenly divide cupcake batter between the lined cupcake pan. Bake for 18-20 minutes, let cool completely.
In a large bowl with a mixer, beat softened butter with powdered sugar, milk, and vanilla extract until smooth. Divide frosting between three bowls. Leave one bowl white, mix red food coloring into one, and blue food coloring into the last bowl.
Arrange cooled cupcakes into a rectangle. Evenly spread the white frosting onto the bottom three cupcakes. Frost two in the middle with red frosting. Frost the top two cupcakes white. Frost the remaining four cupcakes with the blue frosting. Pipe remaining white frosting onto blue cupcakes.
