Wash the green seedless grapes thoroughly and dry them completely. Any moisture will prevent the candy from sticking. Place 3-4 grapes on each skewer. Keep the skewers on a tray in the refrigerator so they are very cold.

Prepare a large flat surface like a baking sheet by lining it with parchment paper. Have your gel food coloring and skewers ready.

In a small, deep, heavy-bottomed saucepan, combine the sugar, light corn syrup, and water. Stir gently to dissolve the sugar. Avoid touching the sides of the pan to prevent crystallization.

Insert the digital candy thermometer, ensuring it does not touch the bottom. Place the pan over medium heat and bring the mixture to a boil. Do not stir.

Wipe down the inside of the pan with a wet pastry brush if sugar crystals form. Heat the syrup to exactly 300°F (149°C) (hard crack stage). This takes 10-15 minutes.

Once it reaches 300°F, remove from the heat immediately. If using flavor extract, stir it in. Keep the pan warm in a bowl of very hot water.

To create the galaxy effect, quickly add single drops of your desired gel food colors directly into the hot, viscous candy base. DO NOT MIX. Gently drag a skewer or knife through the dots to form swirled marbles.

Working one skewer at a time, quickly dip the cold grapes into the swirled candy mixture, turning the stick as you dip to evenly coat the fruit. Let the excess candy drip off.

Place the coated skewers flat on the prepared parchment paper. The candy shell will set within minutes on the cold grapes. Serve immediately for best quality.