01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - Whisk together flour, baking soda, baking powder, and salt in a medium bowl. Set aside.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy, approximately 2 minutes.
04 - Add egg and vanilla extract, beating until well incorporated.
05 - Gradually mix dry ingredients into wet ingredients until just combined.
06 - Divide dough evenly between two bowls. Add one Jello flavor to each bowl (about 3 tablespoons per bowl) and knead until color and flavor are thoroughly incorporated.
07 - Scoop tablespoon portions of dough, roll into balls, then coat in extra granulated sugar.
08 - Place cookies 2 inches apart on prepared baking sheets.
09 - Bake for 8 to 10 minutes, until edges are set but centers appear slightly underbaked for optimal chewiness.
10 - Let cookies rest on baking sheet for 5 minutes, then transfer to wire rack to cool completely.