Chill your martini glass with some ice and then fill a shaker with ice.
Add 2oz Bacardi Limon Rum, .5oz Patron Citronage, .25oz Fresh Lime Juice, and 1.5oz White Cranberry Juice and shake vigorously.
Once cold, empty your martini glass and strain the cocktail into it. Slowly pour .25oz Blue Curacao down the side of the glass allowing it to sink to the bottom.