Stir together the water, sugar, and corn syrup in a medium sized saucepan.
Clip the candy thermometer to the side of the pan, and boil over medium heat (stirring very frequently) until the temperature reaches 300 degrees.
Remove from heat and CAREFULLY pour 1/3 of the the hot sugar mixture into each of the two Pyrex measuring cups. Immediately add food coloring and flavor oil to the remaining liquid in the saucepan as well as the measuring cups. Stir well.
Pour the contents on to a non-stick mat and allow to cool completely.
Use a food-safe hammer to break the hardened candy into smaller pieces.
Put the pieces in a large plastic zipper bag along with the powdered sugar, and shake to coat. Use your fingers to brush off the excess sugar.