Remove the corn cobs and strain the corn liquid through a fine-mesh strainer. Ladle about 3 1/2 cups of liquid and either discard the rest or save for another time. Pour the 3 1/2 cups of corn liquid back into the large pot and stir in the powdered fruit pectin. Bring to a boil.
Stir in about 4 cups of sugar and bring to a rolling boil once again. Skim off any foam from the top of the mixture and discard. Add yellow food coloring if desired.
Ladle the corn liquid into jelly jars and be sure to leave about a 1-inch headspace. Seal the jars and place in a water bath for 10-15 minutes.
Remove the hot jars from the water bath and allow to cool. Keep an ear out to listen for any jars that might pop. If they pop, the jars will last for 1-2 years. If they do not pop, no worries. Just place the corn cob jelly jars in the refrigerator and use within 2 weeks.