Preheat your oven to 350°F (175°C).
Grease and flour six 8-inch round cake pans.
In a bowl, mix flour, baking powder, and salt.
In a separate 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 the flour mixture, alternating with milk.
Divide the batter into six bowls and add different food coloring to each.
Pour each colored batter into the prepared pans.
Bake for 25-30 minutes until a toothpick comes out clean.
Let the cakes cool completely before frosting.
Layer the cakes with buttercream frosting between each layer.
Frost the outside and decorate as desired.