Combine tequila, blue curacao, coconut milk, and lime juice in a blender.

Cover and blend on high speed.

Gradually add frozen raspberries, frozen blueberries, and ice.

Whirl until the margarita mixture is smooth and slushy.

In a small bowl, mix sugar and lavender blossoms.

Rub the mixture with your fingers or mash with a spoon.

Moisten glass rims with a lime wedge.

Dip the rims in the lavender sugar, coating evenly.

Pour the margaritas into the sugar-rimmed glasses.

Garnish with lavender sprigs (optional).