Classic shortbread gets a colorful update here, making it perfect for a wedding or shower favor.
Put butter and sugar in the bowl of an electric mixer. Mix on medium speed until pale and fluffy, 2 to 3 minutes. Mix in extracts and salt. Reduce speed to low; slowly mix in flour until dough starts to come together (do not overmix).
Turn out dough onto a lightly floured surface; knead just to bring together. Divide dough into 5 balls of various sizes. Knead varying amounts of pink food coloring into 4 of the balls to tint dough various shades of pink.
Place each ball between 2 sheets of lightly floured parchment paper; roll out to 5-inch squares. (Squares will be of varying thicknesses.) Trim edges of squares with a knife to make straight. Freeze squares on parchment paper on baking sheets 20 minutes.
Whisk together egg white and 1 tablespoon water in a small bowl. Brush egg wash over surface of 1 square. Top with another square; brush with egg wash. Continue stacking remaining squares, alternating colors and thicknesses, and brushing with egg wash between each layer. Let assembled block of dough stand until it reaches room temperature. Trim sides with a sharp knife to make straight.
Preheat oven to 325 degrees. Using a long sharp knife, slice block into 1/4-inch-thick strips (you should have about 20 strips of dough). Cut each strip in half crosswise to make 40 (2 1/2-inch-long) cookies. Transfer, striped side up, to baking sheets lined with parchment paper; freeze until firm, about 30 minutes.
Bake until edges turn golden, about 15 minutes. Let cool on sheets on wire racks.