Preheat the oven to 350°F (175°C) and grease and flour three 9-inch round cake pans.

In a large mixing bowl, cream together the softened butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.

In a separate bowl, sift together the flour and baking powder. Gradually add this to the wet mixture, alternating with milk, and mix until just combined.

Divide the batter equally into two bowls. In one bowl, add a few drops of blue food coloring and mix until the desired hue is achieved; in the other bowl, replicate with pink food coloring.

Pour the blue batter into one of the greased pans and the pink batter into another, leaving the third pan with the original vanilla batter.

Bake in the preheated oven 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 wire racks to cool completely.

Once cooled, stack the cakes by alternating colors to ensure the surprise stands out. Frost the entire cake with whipped cream and decorate with sprinkles.