Spray a 9-inch by 13-inch cake pan with baking spray.
Optionally, line the pan with parchment paper and spray the paper.
Divide white cake batter into 6 bowls (about 3/4 cup in each).
Color one bowl red, another orange, yellow, green, blue and purple.
Pour batter into individual disposable pastry bags or large zip top bags.
Snip off the tip of the bag and pipe squiggles of one color batter into the pan.
Use about 1/3rd of the batter for the first layer.
Continue piping squiggles of colors, layering the 6 colors a total of three times.
Tap the pan on the counter a few times to level the cake batter and to remove any air bubbles.
Bake according to instructions on the cake mix box.
Remove cake and allow to cool completely.
Invert cake onto a cutting board.
Remove parchment paper if necessary.
Cut cake in half so you have two 9 by 6 1/2-inch pieces.
One piece will be the unicorn's body.
Cut the other piece in half so you have two 6 1/2 by 4 1/2-inch pieces.
One piece will be the unicorn's head.
Cut two 2 by 3-inch pieces for the unicorn's legs.
Assemble the cake by placing the 9-inch by 6 1/2-inch cake in the lower half of your cake board forming the unicorn's body.
Set the 6 1/2-inch by 4 1/2-inch piece about 2 1/2 inches from the top edge of the larger cake forming the unicorn's head.
Roll the remaining white candy clay to about 3/16-inch thickness. Cut out an ear using a 1 1/2-inch wide by 2 1/2-inch long teardrop cookie cutter or a knife.
Roll out the pink candy clay to about 1/16th-inch thickness.
Cut a smaller teardrop shape.
Use a small dab of water to attach the pink teardrop to the center near the lower edge of the white teardrop to form the unicorn's ear.
Roll out the black candy clay and cut out a 2 1/4-inch circle then cut just a thin edge from around the circle to create a thin moon-shaped eye.
Cut a small 3/4-inch round out of the black and do the same creating a nose.
Rainbow Unicorn Cake https://hungryhappenings.com/rainbow-unicorn-cake/