Bake and cool cakes. Position cakes on cooling grid over waxed paper-covered cookie sheet.
Tint portions of icing yellow and orange; leave some white. Heat in microwave at defrost setting (30% power) for 20-30 seconds; stir. Repeat until consistency of icing will pour.
Using decorating bags with 1/4 in. cut from tips, cover cakes with white icing on top, orange icing in middle and yellow icing on bottom until completely coated. Lightly tap grid to spread. Sprinkle each section with corresponding sugars. Let set.