Line an 8x8x2-inch baking pan with foil, extending foil over edges of pan. Oil or butter foil; set pan aside.
In a heavy 2-quart saucepan, combine sugar, corn syrup, and water. Cook and stir over high heat until mixture boils. Clip a candy thermometer to side of pan.
Continue cooking over medium heat, stirring occasionally, until thermometer registers 300 degree F (hard-crack stage). Remove thermometer from pan; remove pan from heat. Add the desired flavoring and coloring. Immediately pour mixture into prepared pan. Let stand for 5 to 10 minutes or until a film forms over the candy surface.
Using a broad spatula, mark candy surface in 1/2-inch squares. Do not break film on surface. (If candy doesn't hold its shape, it isn't cool enough to mark. Let stand a few more minutes.)
Retrace previous lines, pressing spatula deeper each time, but not breaking the surface until the spatula can be pressed to the bottom along all lines. (If candy hardens before the pieces are cut, put it in a warm oven for a few minutes.)
Cool completely. Use foil to lift the candy out of the pan; break candy into squares. Roll candy pieces in powdered sugar; shake off excess. Makes 1 pound candy.
