In a large heavy saucepan, combine sugar, water and corn syrup. Bring to a boil over medium heat, stirring occasionally. Cover and cook for 3 minutes. Uncover and cook over medium-high heat, without stirring, until a candy thermometer reads 310° (hard-crack stage). Remove from the heat; stir in oil and food coloring, keeping face away from the mixture as the odor with be very strong.
Immediately pour onto a greased baking sheet. Quickly spread into a 13-in. x 9-in. rectangle. Using a sharp knife, score into 1-in. squares. Re-cut rectangle along scored lines until candy is cut into squares. Let stand at room temperature until dry. Separate into squares, using a knife if necessary. Yield: 1 pound.