Preheat your oven to 350°F (175°C) and grease six 8-inch round cake pans.
In a bowl, whisk together flour, baking powder, and salt.
In another bowl, cream butter and sugar until light and fluffy.
Add eggs one at a time, mixing well after each addition.
Stir in vanilla extract.
Gradually add flour mixture and milk, alternating until combined.
Divide the batter evenly into six bowls.
Add different food coloring to each bowl to create six colors.
Pour each colored batter into prepared pans.
Bake for 25-30 minutes, or until a toothpick comes out clean.
Allow cakes to cool before frosting with buttercream.