Preheat oven to 350 degrees. Beat butter and sugar at medium speed with an electric mixer until creamy. Add eggs, 1 at a time, beating until blended after each addition. Combine flour, baking powder, and salt; add to butter mixture alternately with milk, beginning and ending with flour mixture. Beat at low speed until blended after each addition. Stir in vanilla.
Place paper baking cups in 2 (12-cup) muffin pans, and coat with cooking spray; spoon batter into cups, filling two-thirds full. Bake for 12-15 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans to wire racks, and cool completely.
To prepare Vanilla Frosting, beat first 4 ingredients at medium speed with an electric mixer until creamy. Gradually add powdered sugar, beating at low speed until blended. Beat at high speed 2 minutes or until creamy. Make 3 cups.
Divide frosting into two bowls. Using food coloring gels, tint 1 bowl of frosting pale pink and 1 bowl of frosting pale blue, stirring until blended.
Frost 12 cupcakes pink and 12 cupcakes blue. Roll edges of cupcakes in white sprinkles. Top with baby shower decorations. (We like onesies, baby faces, and baby booties.)