Preheat oven to 350 degrees. Line a cupcake pan (two if you have them) with white paper liners.

In the bowl of a stand mixer fitted with the paddle attachment, beat the butter until well creamed. In a small bowl combine the sugar and the seeds from ½ vanilla bean. Mix together with your fingers until the vanilla beans are well dispersed into the sugar. Add the sugar mixture to the butter and beat until light and fluffy. Add the eggs one at a time beating well after each addition.

Whisk together flour, baking soda, baking powder and salt, set aside. In a medium sized bowl, whisk together ½ cup pineapple juice and ½ cup sour cream. Add flour mixture and pineapple juice mixture alternately, beginning and ending with flour.

Divide the batter evenly between 4 medium bowls. Tint one bowl of batter red, one orange and one yellow with the gel food colors; leave one bowl untinted. Stir the coconut extract into the red batter, Stir the orange extract into the orange batter. Stir the pineapple oil into the yellow batter.

Transfer each batter to disposable piping bags or zip-top bags. Snip the tip of the piping bag and pipe the red tinted batter evenly into the bottoms of each cupcake liner. Repeat process using the orange next, then the yellow and finally the plain batter.

Bake for 17-22 minutes, or until the cakes spring back when pressed in the centers. Allow the cupcakes to cool completely.

In the bowl of a stand mixer fitted with the whisk attachment, cream softened butter and powdered sugar together. Add the vanilla seeds; beat again until the frosting is thick and fluffy. Scrape down the sides of the bowl and beat again briefly.

Transfer the frosting to a piping bag fitted with a large star decorator tip and pipe the frosting onto the cooled cupcakes.

Combine the coconut rum and grenadine in a small bowl. Fill pipettes with the rum mixture. Insert the pipettes into the cupcakes up to 3 hours before serving.