Which liqueur is primarily used in a Midori Sour?

The Midori Sour prominently features Midori, which is a bright green, melon-flavored liqueur. This liqueur is known for its vibrant color and sweet taste, making it the ideal base for the cocktail. The distinct flavor of Midori provides the primary character of the drink, complemented by other ingredients such as sour mix or lemonade, which balances the sweetness with acidity.

In contrast, the other liqueurs mentioned do not play a role in a Midori Sour. For instance, Peach Schnapps lends a peach flavor that would not align with the melon profile of the cocktail. Triple Sec, an orange-flavored liqueur, is commonly found in many cocktails, but it does not contribute to the specific taste of a Midori Sour. Amaretto, with its almond flavor, would also detract from the intended flavor combination that Midori offers. Therefore, Midori is undeniably the central component of a Midori Sour, making it the correct response.