A clear indicator of a cocktail's rising popularity is when there are abundant contemporary variations of the same. This suggests that the drink is being consumed by a large number of people, albeit in different forms. An even clearer sign is, when a whiskey drink is reimagined, given that traditionalists have typically dismissed whiskey-based cocktails for purportedly diluting and altering the purity of whiskey. 

Rob Roy is arguably one of the most popular whiskey-based cocktails today. And Blue Rob Roy slightly tweaks the original Rob Roy recipe, by exclusively using Johnnie Walker Blue label whiskey in its making. This variant is comparatively newer, since the alcohol itself was launched only in the 1980s. 

The Blue label Scotch is supposedly crafted with whiskeys that have been aged for up to 60 years, as opposed to the Black Label Scotch, the slightly lesser nuanced blended whiskey. The drink has discernable toffee notes accompanied by a subtle hint of smokiness. While there are grassy undertones, chocolate and full-bodied malt flavours round out the overall profile. In  comparison, the herbal notes in Black Label whiskey are more pronounced, and have a woody and a dry spice aroma. 

The original recipe of Rob Roy was itself a variation of a New York classic, Manhattan, that emerged in - you guessed it - New York during the late 1870s. Made with sweet vermouth, bitters and rye whiskey that was local to the US, this drink was an instant classic. As Scotch whiskey left Scotland’s shores in the early 1930s, rye whiskey began being replaced by this new velvet smokey whiskey blend. Legend has it that Rob Roy was conceived at the iconic Waldorf-Astoria  Hotel in New York. However, an alternate version of its creation has been offered by cocktail historian David Wondrich, who claims that the drink was created in New Jersey in 1895, at a restaurant named Duke’s House, situated just across from the Manhattan ferry. 

The story goes that a salesman peddling blended Scotch whisky once walked in, desiring a Manhattan. However, adhering to his company's ethics, he couldn't indulge in anything not featuring their own whisky. The bartender, a certain Henry A Orphal, ingeniously resolved the dilemma by substituting 2 ounces of Scotch for the traditional ingredients of rye whiskey. 

Regardless of its originator or birthplace, the Rob Roy swiftly captured the American palate, becoming a widely requested libation throughout the entire country. The drink's popularity may have been further propelled by the familiarity of Rob Roy as a prominent figure in New York during that era. It's worth noting that some accounts suggest the cocktail was crafted in homage to the debut of Rob Roy, an operetta composed by Reginald De Koven and lyricist Harry B. Smith in the late 1890s.