Preheat the oven to 350 degrees. Line your cupcake pans with your choose of cupcake wrappers.

Place your self-rising flour, cake flour, and sugar in the bowl of your mixer. Mix them together for a minute or two until they are well combined.

Cut your butter into tablespoon pieces. Slowly add your butter into the flour mixture one piece at a time continue mixing until you have reached the texture of sand.

Pour half of your milk into the flour mixture and mix just until the milk is incorporated. Use your rubber spatula to scrape down the sides of your bowl. Add your remaining milk and the vanilla to your batter and mix until combined.

Slowly add in one egg at a time to the cake batter, making sure each egg is incorporated before adding the next egg.

Scoop the batter into the prepared cupcake pan, filling them 3/4 of the way full.

Bake for 10 minutes then rotate the cake pans so the pan that was on the top rack is now on the bottom and the pan that was on the bottom is now on the top rack. Continue to bake for another 10-13 minute until a toothpick comes out clean from the center of the cupcake.

Place your butter and shortening together in the bowl of your mixer. Mix them together on medium speed until they are nice and creamy.

Turn the mixer down to the lowest setting and slowly incorporate the powdered sugar into the shortening mixture.

Once you have added all the powdered sugar in to your mixture, add in the vanilla extract and then the hot water.

Turn the mixer up to medium-high speed and continue mixing for 10 minutes until light and fluffy.

Bake your cupcakes and allow them to cool completely. While the cupcakes are cooling make your frosting.

Divide your buttercream into four equal parts into four bowls. Using your food coloring, color one part blue, one part purple, one part pink and one part yellow.

Place a large piping tip into your pastry bag. Working in small batches scoop the blue buttercream into one side of the pastry bag keeping room for the other colors.

Place some of the purple buttercream next to the blue buttercream.

Place some of the pink buttercream next to the purple buttercream.

Finally place some of the yellow buttercream next to the pink buttercream.

You should end up with each color of the buttercream next to each other in the pastry bag.

Twist the open end of the pastry bag to push the frosting to the tip to make sure that the colors have intertwined.

Begin frosting the cupcake on the outside edge then work to the center of the cupcake.

Refill the bag as need in the same way you filled it the first time.