Body language
Green monkeys are known to communicate both verbally and non-verbally. They have distinct calls which they use to warn others in the group of predators, and even have specific calls for specific predators. Body language, such as the display of brightly colored genitalia is also used to communicate danger, but can also be used as a way of establishing dominance. It has also been documented that green monkeys may use facial expressions to express their emotional state.