Spray a 6-cup Bundt pan with baking spray with flour.
In a medium bowl, combine cake flour, baking powder, baking soda, and salt, whisking well.
In a large mixing bowl, combine butter and granulated sugar. Beat at high speed with a mixer until light and fluffy, approximately 3 minutes. Add eggs and egg yolk, one at a time, beating well after each addition. Add vanilla extract, beating until blended. Add flour mixture to butter mixture in thirds, alternately with ½ cup milk, beginning and ending with flour mixture.
Pour batter into prepared pan, and tap on countertop to settle batter and reduce air bubbles.
Bake until a wooden pick inserted in the center of cake comes out clean, approximately 40 minutes. Let cake cool in pan for 10 minutes.Turn cake out onto a wire cooling rack, and turn cake right side up. Let cool completely.
In a large bowl, combine confectioners’ sugar and remaining 2½ tablespoons milk, whisking until smooth. Divide mixture into 3 bowls. Using food coloring, tint a portion green, a portion yellow, and a portion pink. Place each color in a piping bag fitted with a medium round piping tip (Wilton #12). Pipe glazes onto cake in stripes.
Store cake in an airtight container at room temperature until serving time, up to 3 days.
Recipe by TeaTime Magazine at https://teatimemagazine.com/striped-vanilla-bundt-cake-recipe/