Make mini cakes. Prepare batter following recipe directions. Bake and cool mini cakes according to pan package directions.
Cover mini cakes in icing. Tint portions of icing violet, blue, green, orange, rose and yellow. Heat yellow icing in microwave at defrost setting (30% power) for 20-30 seconds; stir. Repeat until consistency of icing will pour. Place mini cakes on cooling grid positioned over parchment paper-lined cookie sheet. Pour icing over cakes; tap grid gently to settle icing. Let set 1 hour.
Decorate mini cakes. Use tip 47 with smooth band side up and violet icing to pipe two stripes across mini cakes. Use tip 3 and blue icing to pipe wavy lines over stripes. Use tip 3 and green icing to pipe dots in between lines.
For circles, use tip 3 and orange icing to outline circles. Use tip 3 and rose icing to fill in circles. Pat smooth with finger dipped in cornstarch.