Grapefruit Jelly

3 cups grapefruit juice (fresh or canned)
4 cups granulated sugar
1 (1.75 ounce) box pectin
3 drops red food color

Add pectin to juice and bring to a boil. Add sugar and bring to a rolling boil for 1 minute. Add food color. Skim and pour into six 6-ounce jars. Skim again and seal.