Color the buttercream

• Divide the buttercream between bowls, one per shade.
• Tint each portion with a different shade of purple food coloring and mix until evenly colored.

Spread the buttercream on cling wrap

• Lay a sheet of plastic wrap flat on the work surface.
• Spread the colored buttercreams side by side in stripes, touching each other.

Roll and remove air bubbles

• Roll the plastic wrap up tightly into a log.
• Press gently with your fingers on all sides to push out the air bubbles, repeating a couple of times.

Fill the piping bag

• Fit the piping tip into the piping bag.
• Cut off one end of the buttercream log and place the rolled buttercream into the bag.
• Twist the top of the bag to close it.

Pipe the swirls

• Pipe a swirl of buttercream on each cooled cupcake, keeping steady pressure to reveal the multicolored effect.