One can of limeade into a blender; fill the can with Tequila and add to the limeade; half fill the can with Grand Marnier; take 2 cups of blackberries, heat in a pan to get the juice out and then strain; add one cup; fill blender with ice; Blend and voila.... you have this dark purple concoction...
A whole can of limade can be too sweet. You may want to start with 3/4 of the can only.