Cut corn kernels from cobs and reserve for another recipe. In a stockpot, place corncobs and water; bring to a boil. Cook, uncovered, 10 minutes.
Discard cobs; strain liquid through cheesecloth. Liquid should measure 3 cups. Add additional water if necessary.
Return to stockpot and stir in pectin. Bring to a full rolling boil. Add sugar and bring back to a boil. Skim foam and add a few drops of food coloring. Transfer to covered jars; refrigerate up to 2 weeks.