Colored sanding sugar is used in and on cookies to add visual appeal and a uniqueness in texture. The colorful crystals provide a decorative touch! Plus, this type of sugar doesn’t melt as easily when baked, ensuring the color and sparkle remain vibrant. 

Sanding Sugar Vanilla Sugar Cookies 

Ingredients 

• 1 ½ cups all-purpose flour
• 1 tsp. baking powder
• 1 tsp. cream of tartar
• ½ tsp. baking soda
• ½ tsp. salt
• ½ cup butter, room temperature
• ¾ cup granulated sugar
• 1 Tbsp. vanilla bean paste
• 1 large egg
• 1 tsp. vanilla extract
• ½ – 1 cup colored sanding sugar, divided

Directions

1. Beat the butter and sugar together in the bowl of an electric mixer using the paddle attachment.  Once butter and sugar mixture is fluffy, add in the vanilla bean paste, along with the egg and vanilla extract.  Beat until thoroughly combined (the mixture will look a little curdled: this is fine!)
2. Reduce the mixer speed to low and slowly add the flour, baking powder, cream of tartar, baking soda, and salt.  The dough will be pretty thick. Add in 1/4 cup of the colored sanding sugar. 
3. Use a medium cookie scoop (1.5 tablespoons) to scoop up the dough and roll it into a ball.  Roll the ball in a bowl with the remaining sanding sugar.  Place the balls on a plate and refrigerate overnight.
4. The next day, bake on parchment-paper lined cookie sheets at 350F for approximately 8 minutes, until cookies spread but are still pale and soft in color.  Allow the cookies to cool on the sheet for 5 minutes before transferring to wire racks to cool completely.

Source: https://www.bunsenburnerbakery.com/sanding-sugar-vanilla-sugar-cookies/