Tint 48 oz. fondant yellow, 44 oz. light rose, 9 oz. pale blue and 9 oz. light green. Brush cake base with piping gel; roll out yellow fondant 1/8 in. thick and cover cake base.
Bake and cool 2-layer 6-in. and 10-in. round cakes. Stack cooled small cake layers on same size cake circle. Stack cooled large cake on fondant cover cake base. Prepare for fondant by lightly icing with buttercream. Prepare for stacked construction.
Cover 6-in. cake with yellow fondant; smooth. Cover 10-in. cake with rose fondant; smooth. Cover cakes with plastic wrap when not decorating them.
Roll out blue and green fondant 1/8 in. thick. Cut into 1-in. squares using ruler and cutter/embosser. Place squares, alternating colors, on cake sides, attaching with damp brush. Stack on large cake. Make one yellow and one rose fondant rope each about 21 inches long; twist and place on bottom of small cake, securing with damp brush.
Roll remaining rose fondant into balls; arrange on large cake bottom border. Roll out remaining fondant 1/8 in. thick. Cut different sized hearts; attach to large cake with damp brush, overlapping and stacking, if desired. Dust both layers and decorations with white pearl dust. Add toppers.