Preheat the oven to 350°F (175°C). Grease and flour six 6-inch round cake pans.

In a large mixing bowl, combine flour, sugar, baking powder, and salt.

Add softened butter, eggs, vanilla extract, and milk. Beat with an electric mixer until smooth.

Divide the batter evenly into six bowls. Add different food coloring to each bowl to create six colors.

Pour each colored batter into the prepared cake pans.

Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then transfer to a cooling rack to cool completely.

In a mixing bowl, beat the softened butter until creamy.

Gradually add powdered sugar, vanilla extract, and milk. Beat until fluffy.

Place the first layer of cake on a serving plate and spread frosting on top. Repeat with remaining layers.

Cover the entire cake with frosting and smooth the sides.

Decorate with sprinkles or additional frosting as desired.