A strong green whiskey kept behind the bar in Ten Forward, which Data offered to Montgomery Scott when the engineer rejected synthehol and could describe only by its colour.
Aldebaran whiskey is a potent alcoholic drink of a vivid green colour. Guinan keeps a small private stock of real liquor aboard the Enterprise-D, including a bottle given to her by Captain Picard.
The drink features in the Next Generation episode Relics. Scotty, rescued after seventy-five years in a transporter buffer, is disgusted to find that Ten Forward serves synthehol in place of Scotch. Data finds him something from Guinan's shelf, and when asked what it is, examines the bottle and can say only that it is green.
Scotty takes the bottle to a holodeck recreation of his old bridge, where Picard joins him for a glass, names the whiskey and admits that he supplied it.