Frost entire cake with same colors. If desired, place remaining black frosting in resealable plastic freezer bag and cut small bottom corner off bag to pipe frosting. To extend guitar neck 1 to 2 inches onto body of guitar, pipe and fill in neck with black frosting. With white vanilla frosting, pipe and fill in contrasting design on body of guitar. On white design, pipe black rectangle about 1 inch from end of neck to create pickup. With gray frosting, pipe on frets, bridge and any additional accents as desired. For strings, add black licorice. Add small fruit candies at ends of strings. For tuning pegs, add gumdrops. For buttons on body, add tropical fruit candies.