Preheat the oven to 350°F (175°C). Grease and line the bottom of the three 9-inch round cake pans with parchment paper.

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy using an electric mixer or whisk.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

In another bowl, combine the flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, alternating with the milk. Mix until just combined.

Divide the cake batter into three equal portions. Add different pastel food coloring to each portion and mix until you achieve your desired colors.

Pour the colored batter into the prepared cake pans and smooth the tops with an offset spatula. Bake in the preheated oven for 20-25 minutes or until a toothpick inserted in the center comes out clean.

Once baked, allow the cakes to cool in the pans for about 10 minutes before transferring them to a cooling rack to cool completely.

For the frosting, beat the softened butter in a bowl until creamy. Gradually add the powdered sugar, mixing well. Then, add the vanilla extract and enough milk to achieve a spreadable consistency.

Once the cakes are cool, place one layer on a cake stand or serving plate. Spread a generous amount of frosting on top. Add the second layer and repeat the process. Top with the third layer and frost the top and sides of the cake.

Decorate the cake with edible decorations such as sprinkles, chocolate eggs, or edible flowers to enhance the Easter theme.