Mix butter and sugar in a bowl until fluffy. Add eggs, mix again, and then add vanilla.
Sift flour, baking powder, and salt together in a separate bowl. Also, if you haven't already, measure out the milk and the Red Bull (you can mix them into the same measuring cup, but it looks a little funky.).
Alternate between adding the dry ingredients and wet ingredients to the batter. Add food color to your heart’s desire.
Fill your cupcake pan with batter.
Bake for 20 minutes, then let cool. Brush tops with more Red Bull, if desired.
For the frosting:.
Cream butter, add half the red bull, then add powdered sugar 1/2-1 cup at a time, mixing as you go.
Add the rest of the Red Bull for flavor/consistency as desired.
Add icing coloring as desired to achieve a bright blue.