Meanwhile, in 1-quart saucepan, combine gelatin, 1/2 cup of the sugar, the lime juice, water and egg yolks. Cook over medium heat 6 to 7 minutes, stirring constantly, until mixture boils and thickens slightly. Remove from heat; stir in lime peel and food color. Pour mixture into large bowl. Refrigerate until mixture mounds slightly, about 45 minutes.