Prepare the Cupcakes:

1. Preheat oven to 350°F (175°C) and line a cupcake tin with paper liners.
2. In a bowl, whisk together flour, baking powder, and salt. Set aside.
3. In a separate bowl, cream butter and sugar until light and fluffy.
4. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
5. Alternate adding the flour mixture and milk to the butter mixture, beginning and ending with flour. Mix until just combined.
6. Divide batter evenly among cupcake liners.
7. Bake for 18-20 minutes, or until a toothpick inserted into the center comes out clean. Let cool completely.

Prepare the Buttercream:

1. Beat butter until creamy. Gradually add powdered sugar and mix until fluffy.
2. Add vanilla extract and heavy cream, mixing until smooth.
3. Divide the frosting into two bowls. Tint one with pink food coloring and the other with green.
4. Transfer each color to a piping bag fitted with a star tip.

Decorate the Cupcakes:

1. Pipe a generous swirl of pink or green buttercream onto each cupcake.
2. Sprinkle with colorful pastel sprinkles for a festive touch.