Fit decorating bag with large petal tip. Fill bag with violet frosting; pipe frosting starting at base of cake using slow even up and down long zigzag motion to create loose ruffle around bottom. Pipe 3 complete rows of violet ruffles, one row on top of another, going up side of cake. Fill same bag with darker pink frosting, repeating to create 3 complete rows of darker pink ruffles. Repeat steps with lighter pink frosting. When all 9 rows of ruffles are piped, squeeze any remaining colored frosting out of bag onto cake.