Green label whiskeys are pulled from barrels stored on the lower floors of a warehouse where the cooler temperatures mature the spirit more slowly. This leads to a lighter, mellower flavor profile than what you’d expect from a bottle of full-bodied black label. In some cases, green label whiskey is bottled at a lower ABV (alcohol by volume) than its black label counterpart.
Professional tasting plays a role in the selection process, too. If a barrel sample doesn’t meet the high standards of the flagship black label bottling, you better believe it’s getting a green sticker slapped on it.