Place cabbage in a large heatproof bowl. Pour boiling water over cabbage and let sit until water turns deep blue, 5 minutes. Strain out cabbage and let water cool.
When water is no longer hot, transfer to ice trays. Freeze until solid, 4 hours.
In a medium pitcher or measuring cup, combine tequila with triple sec, lime juice, and lemonade. Wet rims of glasses with a lime wedge and dip in salt.
Place purple ice cubes in glasses and divide margarita between them. Garnish with a lime wedge and serve.
Recipe by The Best Video Recipes for All at https://recipes-for-all.com/color-changing-margaritas/