Curaçao (/ˈkjʊərəsaʊ/ KEWR-ə-sow) is a liqueur flavored with the dried peel of the laraha citrus fruit, grown on the island of Curaçao. A non-native plant similar to an orange, the laraha developed from the sweet Valencia orange transplanted by Spanish explorers. The nutrient-poor soil and arid climate of Curaçao proved unsuitable to Valencia cultivation, resulting in small, bitter fruit of the trees. Although the bitter flesh of the Laraha is all but inedible, the peels are aromatic and flavorful, maintaining much of the essence of the Valencia orange.
Curaçao liqueur was first developed and marketed by the Senior family in the 19th century. To create the liqueur the laraha peel is dried, bringing out the sweetly fragranced oils. After soaking in a still with alcohol and water for several days, the peel is removed and other spices are added.
The liqueur has an orange-like flavor with varying degrees of bitterness. It is naturally colorless, but is often given artificial coloring, most commonly blue or orange, which confers an exotic appearance to cocktails and other mixed drinks. Blue color is achieved by adding of food colorant, most often E133 Brilliant Blue.
A common question is hey, what's the difference between and triple sec and orange curaçao? Camper English of Alcademics has a good answer:
Four hundred years ago, the Dutch were some of the world’s greatest traders and, not coincidentally, great distillers. They’d preserve the spices, herbs, and fruit brought home on ships in flavored liqueurs and other spirits. Curacao was one of those liqueurs, flavored with bitter orange peels from the island of the same name. At the time, the liqueur would have had a heavy, pot-distilled brandy as its base.
Then the French came along (a couple hundred years later) and invented triple sec. The “sec” meaning “dry,” or less sweetened than the Dutch liqueur. The origin of the “triple” is still up for debate, but the two leading schools of thought are “triple distillation” versus “three times as orangey”. Triple sec was also clear, whereas curacaos were dark in color.
Today, triple secs are usually still clear (made from a base of neutral spirits), whereas curacaos may start that way and be colored orange, blue, and even red. Cointreau is probably the most recognized brand of orange liqueur in the triple sec style, and Grand Marnier, despite being French, is more in line with the Dutch curacao style as it has an aged brandy base.