Which cocktail contains both light and dark rum?

The cocktail that contains both light and dark rum is the Zombie. This tropical cocktail is known for its complex flavor, which is achieved by combining various types of rum, including both light rum and dark rum. The use of different rums allows for a depth of flavor that is characteristic of this drink, often enhanced with fruit juices, bitters, and other ingredients.

The Mai Tai typically features only one type of rum, specifically a blend of light and dark rums but not both in substantial amounts like in a Zombie. Meanwhile, the Blue Hawaiian and Chocolate Martini do not traditionally include rum at all, focusing instead on different spirit components and flavors. Thus, the Zombie stands out as the correct answer for containing both light and dark rum.