First, taste the lime juice you squeezed. If it's mildly sour and sweet, it's fine. If it's too sour, use it in another cocktail.

Green pipermint liquor,lime juice,gin into the shaker. shake it. into the glass.

Drop blue curacao. complete.

Use limes with a bright yellow-green peel. Because it's less sour. Rub the lime well before squeezing it, this will reduce the sourness.