Dip the rims of six individual dessert dishes in lime juice, then in sugar; set aside. In a bowl, dissolve gelatin in boiling water. Stir in cold water. Refrigerate until slightly thickened, about 30 minutes. Meanwhile, combine the whipped topping, milk, lime zest if desired and orange extract. Fold into gelatin. Spoon into dessert dishes. Refrigerate for 1 hours or until firm. Just before serving, garnish with cherries and lime zest if desired.