Crust: In a food processor, crush pretzels to a coarse powder. In a medium bowl, mix together crushed pretzels, sugar, and butter. Press crushed pretzel mixture into bottom and sides of a 9-inch pie plate. Refrigerate.
Filling: In a medium bowl, combine sweetened condensed milk, and lemonade drink mix, blend well. Stir whipped topping into pie mixture. Add food coloring and mix to distribute. Pour pie mixture into pie crust. Freeze.