On a cake plate, dab a bit of frosting to anchor the bottom cake layer, the one most deeply colored. Spread with 1/3 cup of white frosting. Top with the layer in the next shade and spread with 1/3 cup of frosting. Top with the last colored layer and spread with 1/3 cup of frosting. Top with the last layer -- the uncolored one. Using about 1 cup of frosting, spread a thin coating over the top and sides of the cake. Place cake in the refrigerator while preparing the colored frosting.
To color the frosting: Measure 3/4 cup of frosting into each of three small bowls, and 11/2 cups into a larger bowl. Add a very small amount of red food coloring to the bowl with the 11/2 cups for frosting and mix well. Add gradually more color to each of the remaining bowls, mixing until you have 4 distinctive shades of pink. Don't be shy; the deepest colored frosting should be a little dramatic.
The frosting rosettes need a Wilton 1M frosting tip. You can use a pastry bag to pipe the frosting, or you can use 4 plastic sandwich bags. Cut off a 1/4-inch tip off one corner, then place the frosting tip in the hole, pressing it halfway through. To fill with frosting, place the bag in a glass, folding the edge over the rim, then fill.
With a ruler and toothpick, mark the layers of the cake into 4 even sections to help you place the rosettes. Starting with the most deeply colored frosting, pipe rosettes around the bottom of the cake using a tight circular, spiral motion. Clean the tip and fill a second bag with the next shade. Pipe another row of rosettes as tightly as possible to the first row, filling any gaps with a dot of frosting. Repeat with the remaining frosting, piping the last, palest shade in 2 batches, around the cake and over the top. Chill for several hours before serving.