Prepare cake batter; divide into thirds and tint each portion yellow, rose and violet, stirring gently. Spray pan with vegetable pan spray. Scoop or spoon different colored batter into pan randomly. Bake 35-40 minutes or until toothpick inserted in center comes out clean. Cool in pan 10 minutes. Remove from pan and cool completely. Position on foil-wrapped cake board cut to fit.
Using spatula, ice cake smooth with yellow buttercream icing; swirl icing with edge of spatula. Add tip 12 white icing to top of cake "layers"; smooth with spatula if needed. Position candy-coated chocolates. Position confetti sprinkles and icing decoration message. Insert candles in cake top.