1. Spray an 8-inch square baking pan with vegetable cooking spray. Dust heavily with confectioners' sugar. In a mixing bowl, sprinkle gelatin over 1/3 cup cold water, and let set 10 minutes.
2. In a saucepan, combine sugar, corn syrup, salt, and 1/3 cup water. Bring to a boil to dissolve sugar, then boil 4 minutes more.
3. With mixer on low speed, pour hot sugar syrup into gelatin. Continue beating until completely mixed. Turn mixer to high and beat 10 to 15 minutes more, until mixture has doubled in volume and is completely white. Beat in vanilla and food coloring, if using.
4. Spread mixture in the prepared pan. Wet hands to smooth top. Let set 3 hours or overnight. Turn onto a cutting board dusted with confectioners' sugar. Cut into squares with a sharp knife. Toss with confectioners' sugar to coat all sticky sides. Store in an airtight container for up to 5 days.