1In small saucepan add lime juice. Sprinkle gelatin over lime juice and let sit for about 1 minute until softened. Place over medium heat for 2 minutes or until gelatin is dissolved, stirring occasionally. Remove from heat and allow to cool slightly (about 4-5 minutes). Add lime peel to saucepan and stir to mix.
2In medium sized bowl pour sweetened condensed milk and food coloring (if used). Pour in lime juice mixture and stir well. Fold in cool whip. Spread into pie crust and refrigerate at least 2 hours. Garnish with sliced lime and additional cool whip, if desired.