Pipe colored stripes.Prepare five 12 in. decorating bags with couplers. Fill separately with purple, pink, teal, yellow and white icing. Fit all couplers with tip 6.
Using ruler and toothpick, mark line around cake 4¼ in. from bottom. Mark second line around the cake 5¾ in. from bottom.
Using white icing bag with tip 6, start at bottom of cake and pipe continuous lines around cake, stopping at 4¼ in. line. Switch to yellow icing with tip 6; pipe one line around cake. Repeat with one line of white icing.
Continue pattern to second marked line with single lines of purple, white, teal, white, pink, white and yellow icing.
At 5 ¾ in. line, switch back to white icing. Pipe continuous lines around remainder of cake and on top. Smooth top of cake with spatula.
With light, even pressure, use icing smoother to smooth sides of cake, cleaning off icing smoother each time. Chill cake for 1 hour.
Reserve remaining yellow, purple, teal and pink icing. Reserve white icing in bag with coupler.