Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a large mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy, about 3-5 minutes.

Beat in one large egg until fully incorporated.

In a separate bowl, whisk the all-purpose flour, baking powder, and salt together until well combined.

Gradually add the dry ingredient mixture to the wet mixture, mixing on low speed until just combined.

Divide the dough into 3-4 equal portions and mix in 1-2 tablespoons of different Jello powder to each portion.

Cover the dough portions and chill in the refrigerator for 15-20 minutes.

Remove the dough, roll it into small balls, and roll in additional sugar before flattening slightly on the baking sheets.

Bake for 8-10 minutes until the edges are set.

Allow the cookies to cool on the baking sheet for 2 minutes before transferring to a wire rack.