Preheat oven to 350°.
Line cookie sheets with parchment paper.
In a large bowl, cream butter until fluffy. Beat in sugar, then add egg and vanilla.
In a small bowl, whisk flour, baking powder, and salt together.
Gradually add flour to butter mixture. It will be crumbly.
Using hands, blend the crumbly dough together until nice and smooth.
Divide into 6 balls.
Add food coloring to desired shade to 5 of the balls, and leave one without added color.
On a floured surface, roll dough to a 1/4" thickness and cut with round cookie cutter.
Cut shapes out of the cookies and interchange the colors. Refer to post for photos.
Sprinkle with sparkling sugar.
Bake at 350° for about 8 minutes.