One week in advance make fondant eggs. Tint 4 oz. fondant each rose, green, blue and violet. Knead in 1/8 teaspoon of Gum-Tex into each color. Use fondant roller with orange guide rings to roll out fondant 1/8 in. thick.
Cut three eggs from each color of fondant. Use wide end of tip 6 to cut out seven circles 1/4 in. from edge and 1/4 in. apart. Save cutouts. Place eggs on cornstarch-covered cake boards. Place different colored cutouts in each egg; reserve remaining cutouts. Let dry overnight.
Bake cake. Prepare batter following recipe directions. Bake and cool. Place on a foil-wrapped cake circle . Prepare buttercream icing following recipe directions. Tint small portion yellow; reserve majority white. Use spatula and white icing to prepare cake for rolled fondant by lightly icing.
Tint 24 oz. fondant yellow. Cover cake with fondant
Make egg topper. Use knife to cut dowel rod to 5 1/2 in. high. Insert into center of cake and cover exposed piece with yellow fondant. Roll a 3/4 in. ball of yellow fondant and place on top of dowel rod.
Melt yellow Candy Melts candy according to package directions. Use melted yellow candy to attach eggs to dowel rod. Each egg should be approximately 2 in. apart at their farthest point.
Decorate cake. Use yellow icing to attach cutouts to side of cake. Use tip 6 and yellow icing to pipe bead bottom border.