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

Cream together the softened butter and granulated sugar until light and fluffy, about 2-3 minutes.

Add in the egg and beat until fully incorporated and smooth, about 1 minute.

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

Gradually add the dry ingredients to the wet ingredients and mix until just combined.

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

Chill the colored dough for 15-20 minutes to firm it up.

Roll the dough into balls and coat each in granulated sugar, then slightly flatten them.

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

Cool the cookies on the baking sheets for 2 minutes before transferring them to wire racks.