Step 1

Position the oven racks in the top and bottom thirds of the oven and preheat to 350 degrees F. Line two baking sheets with parchment paper. Set aside.

Step 2

Whisk together the flour, black cocoa powder, unsweetened cocoa powder, espresso powder, baking powder and salt in a large bowl.

Step 3

Combine the butter, brown sugar and 1/2 cup granulated sugar in the bowl of a stand mixer fitted with the paddle attachment. Beat on medium-high speed until light and fluffy, scraping the sides of the bowl as needed, about 2 minutes.

Step 4

Add the egg and beat until incorporated. Add the vanilla and beat until incorporated. Decrease the mixer speed to low and add the flour mixture a little at a time, beating until just combined. Set aside.

Step 5

Add the violet sanding sugar and the flat purple sprinkles to a food processor and process until dusty and the consistency of powdered sugar, scraping the bowl as needed, about 2 minutes. Add 1/4 cup confectioners’ sugar and pulse just to combine. Transfer to a small bowl and set aside. Wipe the bowl of the food processor clean and repeat with the orange sanding sugar, orange flat sprinkles and the remaining 1/4 cup confectioners’ sugar.

Step 6

Place the remaining 1/2 cup granulated sugar in a medium bowl. Scoop heaping tablespoons of the cookie dough up and roll them into balls (you should have 24 balls). Toss 12 of the balls in the granulated sugar first, then in the purple confectioners’ sugar, coating them very generously and thoroughly. Arrange the balls about 1 inch apart on one of the prepared baking sheets. Repeat with the remaining 12 balls, granulated sugar and the orange confectioners’ sugar. Coat all the balls again in the purple or orange confectioners’ sugar; double coating them will enhance the color.

Step 7

Bake on the upper and lower oven racks until the cookies spread, the tops crack and the edges are firm, 14 to 16 minutes, switching the pans top to bottom about halfway through baking. Let the cookies cool on the baking sheets for a few minutes, then transfer the cookies to a wire rack to cool completely. Store in an airtight container for up to 3 days.