Blend red, green or blue-black grapes in a food processor until a smooth, frothy liquid forms. With a plastic spatula, press mixture through a fine strainer into a mixing bowl. Discard skins and skim foam off the top. Whisk sugar into juice until dissolved. Add a few drops of red, green or purple food coloring if desired.
To make juice pops, fill molds or 5-ounce paper cups with juice, spooning most of the foam off the top. If using cups, cover each cup with foil and insert a wooden stick in the center of the foil. If adding grapes to pops, place approximately 1/4 cup halved grapes into each mold. Pour juice into molds, spooning most of the foam off the top. Place molds or cups in freezer and chill until frozen. To remove bars from cups, take off foil and tear away paper.
Nutritional Stats: 136 Calories; 1 g Protein; 1 g Fat; 34 g Carbohydrates; 0 mg Cholesterol; 2 g Fiber; 4 mg Sodium