In small bowl sprinkle gelatin over water to soften. Let stand 5 minutes. Place bowl in a pan of simmering water and stir until gelatin is dissolved. In large bowl combine lime juice, sugar, milk, lime peel, salt and food coloring. Stir in gelatin. Refrigerate, stirring occasionally until mixture mounds slightly when dropped from a spoon, about 15 minutes. Fold in whipped cream; spoon filling into pie shell. Refrigerate until firm. 30 minutes. Makes 8 servings. 325 calories each.