Frost a thin layer of vanilla buttercream onto the top of the cake and smooth it down with your angled spatula.
Add a thin layer of vanilla buttercream to the sides of the cake and smooth it with your icing scraper until the sides are smooth and even.
Chill the frosted cake for about 20 minutes to let the buttercream set up.
Mix a little Pink into one bowl, a little Blue into another, a mixture of Pink and Blue into the third bowl to make a purple tone, and a few drops of Black in the last bowl for a deep black tone.
Add a few dabs of the pink buttercream to the sides and top of the cake and smooth it all with your icing scraper.
Repeat this process with the purple and blue buttercream until you’ve got a nice watercolor finish on your cake.
Add the black buttercream over the top and smooth it until the colors underneath peek through.
Pop the cake back into the refrigerator for another 15 minutes to let everything set up.
In the bowl of white buttercream, add a few drops of water and mix until it becomes a thick liquid.
Dip your food grade paintbrush into the diluted buttercream and splatter paint it all over the cake.
Add Glitter Stars and Silver Sprinkles wherever desired.
