Line a 17x11x1 jelly roll pan with parchment paper or a silicone mat. Grease with cooking spray.
In a large saucepan, add in sugar and cornstarch. Mix until there are no lumps of cornstarch.
Add in corn syrup, water, and butter. Heat over medium/high heat to 250 degrees. Stir occasionally until the mixture comes up to a boil. As soon as the mixture is boiling, don't stir anymore.
Remove from heat once the mixture is up to 250 degrees. Add in the vanilla and kool-aid mix and stir. I divided the mixture in half and used two different kinds of kool-aid drink mix.
Spread onto the jelly roll pan and let cool for 20 minutes. I let the two different flavors run into each other.
After it's cooled, rip off pieces of the taffy and pull it until it lightens in color. I skipped this process and cut mine into squares with a pizza cutter. I rolled mine up and flattened the ends. Cut small squares of parchment paper and rolled the taffy inside.