Mix together sugar and cornstarch in a heavy bottom sauce pan. Stir in corn syrup, juice, margarine and salt. Bring to a boil, stirring constantly. Cover pan and allow to boil 3 minutes. Check temperature with a candy thermometer. Bring temperature to 250 degrees F, keeping covered as much as possible. When temperature is reached, remove from heat and add flavoring and coloring (you can use whatever flavor/color you desire). Add flour and stir thoroughly. Dump hot candy onto parchment paper and cool until you can handle it comfortably. Pull like taffy about 20 times. Lay back on parchment paper and press flat with the palms of your hands. Roll with a rolling pin to desired thickness--if it gets too cold microwave 10 seconds. Cut with kitchen shears into strips.