Heat oven to 350°F (325°F for dark or nonstick pans). Place paper baking cup in each of 24 regular-size muffin cups.
In small bowl, mix 1 1/2 cups pretzel, 2 T sugar and 1/4 cup melted butter or margarine until blended. Spoon about 1 tablespoon mixture in each cup.
3In large bowl, beat cake mix, margarita mix, water, oil, egg whites and 3 tsp zest with electric mixer on low speed 30 seconds, then on medium speed 2 minutes, scraping bowl occasionally. Divide batter evenly among cups (two-thirds full).
Bake 18 to 23 minutes or until toothpick inserted in center comes out clean. Cool 10 minutes; remove from pan to cooling rack. Cool completely.
In medium bowl, fold whipped topping, yogurt and 2 tsp lime zest until blended; add food coloring if desired and frost cupcakes. Sprinkle with remaining 1/2 cup coarsely crushed pretzels. Store loosely covered in refrigerator.