They should have a glowing orange-brownish color like the whiskey in the game, as Scotch is a type of whiskey. It even shares its world model with "large whiskey bottle", a clutter item that bears "Scotch" on its label but can not be consumed.
Scotch can be obtained freely from Dukov when asked, "Hey can I have some of that hooch?" He then encourages the player to take a Scotch from the upstairs cabinet.
Gob offers kind players a discount on the Scotch he sells.