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

In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy (2-3 minutes).

Beat in a large egg until fully incorporated.

In a separate bowl, whisk together flour, baking powder, and salt.

Gradually add the dry ingredients to the butter mixture, mixing until a soft dough forms (1-2 minutes).

Divide the dough into 3-4 portions, add Jello powder to each and mix until colors are incorporated.

Cover bowls with plastic wrap and chill the dough in the refrigerator for 15-20 minutes.

Roll the dough into 1-inch balls and coat each ball in additional sugar.

Place on baking sheets and slightly flatten each ball before baking.

Bake for 8-10 minutes, until edges are set and tops crack slightly.

Cool on baking sheets for 2 minutes before transferring them to a wire rack.