Pour the tequila, lime juice, blue curacao, and lemonade into a pitcher. Stir to combine, and add 4 to 6 drops of food coloring to adjust the color of the cocktail to your desired hue of purple. Add a handful of ice cubes and refrigerate for one hour.
Prep the glasses:
Prep the rim of your glass by rubbing a lime wedge along the rim. Dip in sanding sugar or tequila salt, and set aside.
Serve & Enjoy:
Fill the glass with a few ice cubes and fill the rest with the purple margarita.