Separate eggs. In top of double boiler beat egg yolks until light colored and thick. Gradually add the sugar and lime juice. Heat 5 minutes over simmering water, stirring often. Set aside to cool. Whip cream and sugar in a chilled bowl.In a small bowl beat eggs at high speed until whites are stiff but not dry. Gently fold beaten egg whites and whipped cream into lime mixture. Stir in grated peel and food coloring. Spoon into graham cracker crust. Freeze until firm.