The first time I heard of a blue coloured cocktail was in the 1988 movie Cocktail, in which Tom Cruise plays a bartender who makes a drink called Turquoise Blue for a patron at his bar. To be frank, the thought of blue drinks has never really appealed to me personally, but when I found out that the recent Giffard West Cup 2019 (Asia Pacific region) had a challenge that required bartenders to come up with a blue-coloured drink, I decided to explore the subject further.
A quick Internet search revealed that many of the more classic blue-coloured drinks tend to be tropical-themed tiki drinks, with the most famous being the Blue Hawaii, made with pineapple juice, blue Curaçao liqueur, coconut cream, and rum or vodka (or sometimes both).