Make ribbon loops for topper two days in advance. Knead 1/2 teaspoon Gum-Tex into 5 oz. white fondant. Tint 1 oz. each: blue, rose, orange, yellow and green. Use 9 in. fondant roller with pink guide rings to roll out tinted fondant, separately, 1/16 in. thick. Use fondant trimmer to cut 25 strips, 1/8 in. x 6 in., in each color. Form each strip into a loop and use damp brush to attach ends. Place loops on their sides to dry on cornstarch-dusted board 24 hours.
Make cake. Prepare batter following recipe directions. Bake and cool cake. Cake is one-layer, 3 inches high. Place on cake board.
Cover cake with fondant. Prepare cake for rolled fondant. Use 20 in. fondant roller with orange guide rings to roll out 18 oz. white fondant 1/8 in. thick. Cover cake with fondant.
Decorate cake. Use tip 4 and white icing to pipe bead border.
Use 1 oz. white fondant to roll a ball, 2 1/2 in. wide x 1/2 in. high. Prepare thinned fondant adhesive following recipe directions. Use thinned fondant adhesive to attach fondant ball to center of cake. Use knife to cut notches in fondant ball. Use thinned fondant adhesive to attach ribbon loops into notches.