Add the tequila, blue curacao and lime juice into an ice-filled shaker. Shake vigorously, taste and add the Sours Mix if desired.
Shake again and strain into a salt-rimmed (optional) martini glass with fresh ice. NOTE: the salt rim can be omitted and the cocktail can be served in a Rocks glass instead).
Making a Pitcher
Combine the tequila, blue curacao and lime juice in a pitcher or glass dispenser. Place in the refrigerator to chill.
Add a few cups of ice or freezeable ice cubes (won't dilute the cocktail) before serving.
Notes
PRO TIP: If Making a PitcherWhen making a pitcher of margaritas using freezeable ice cubes keeps the cocktail cold and doesn't melt diluting or watering down the actual cocktail.