Pour slightly cooled syrup mixture into gelatin mixture; beat on low until combined. Increase speed to high and beat until thick and fluffy and mixture triples in volume, about 10 minutes. Working quickly divide marshmallow mixture into three and mix in food coloring. Using a lightly oiled spatula, scrape all three colored marshmallows into prepared pan. Fold and swirl spatula through mixture to create a marbled effect. Do not over work. Smooth top to an even finish (If top surface is not completely smooth don’t worry about it). Set aside in a cool place, (not the refrigerator) for 8 hours or overnight. Use a serrated knife lightly covered in non-stick spray and slice marshmallows into 1 inch cubes. Cover cut sides with cornstarch and confectioner’s sugar mixture. Marshmallows will keep in an air tight container for up to 5 days.