In a shallow dish that is wider that the rim of your glasses, combine corn syrup and red food coloring. Use a toothpick to mix until the corn syrup is completely red.
In a blender, combine lime sherbet, pink grapefruit juice and club soda. Add vodka to taste for an adult version. Blend until frothy and fully combined, about 10 seconds.
Dip the rim of each glass into the red corn syrup. Turn each glass upright and let the corn syrup drip down the sides.
Pour the punch into the prepared glasses and serve.