Stir 1 cup boiling water into lemon gelatin in medium bowl at least 2 minutes or until completely dissolved. Stir in cold water. Pour into 8-inch square pan. Refrigerate 4 hours or until firm. Cut into 1/2-inch cubes.
Stir 1 cup boiling water into orange gelatin in large bowl at least 2 minutes or until completely dissolved. Stir in orange juice. Refrigerate about 20 minutes or until slightly thickened (consistency of unbeaten egg whites). Gently stir in whipped topping. Gently stir in gelatin cubes and sprinkles. Refrigerate until mixture will mound. Pour into crust.
Refrigerate at least 4 hours or until firm. Garnish with additional whipped topping and sprinkles, if desired.