Step 1Butter a large, rimmed baking sheet.
Step 2In a large, heavy-bottom saucepan, whisk together the sugar and cornstarch. Stir in the corn syrup and water and bring the mixture to a boil over medium-high heat. Continue cooking until a candy thermometer reaches 255 degrees (the mixture will come to a roaring boil and then hold its temperature around 220 degrees for a while; be patient as the thermometer will slowly continue to climb as the water cooks off). Remove the pan from heat and stir in the butter, salt and flavoring until fully incorporated.
Step 3Pour the mixture out onto the prepared baking sheet and add a dozen or so drops of food coloring to the taffy. Set the taffy aside just until cool enough to handle without burning yourself.
Step 4Grease your hands well with butter and gently peel the taffy from the sheet. Begin "pulling" the taffy by stretching it, folding it, and stretching it again. Continue pulling the taffy to distribute the color evenly; as the taffy is pulled, it will lighten in color and become stiff as it cools, 15 to 20 minutes. When the taffy is almost too tough to pull, stretch it into long, skinny strips and cut the strips into bite-sized pieces using a greased knife or greased pair of scissors.
Step 5Wrap each individual piece of taffy in a small piece of waxed paper, and store the candy in a cool, dry place.