PREPARE and bake single pie crust according to recipe directions, using a 9-inch pie plate; cool.
SPRINKLE gelatin over the water in a glass measuring cup.
WHISK together egg yolks, sugar, lime juice, lime peel and salt in small saucepan over medium heat until slightly thickened. Remove from heat.
STIR reserved gelatin and add it to the filling mixture, whisking until smooth. Whisk in food coloring, one drop at a time, until desired color is achieved. Cover saucepan with plastic wrap and refrigerate filling until partially set.
USING a rubber spatula or wooden spoon, gently stir whipped topping into cooled gelatin mixture. Transfer filling mixture to baked pie crust, then refrigerate until firm. Before serving, garnish with lime peel.