She will weigh between 5 and 9 pounds. Monas are masked monkeys. Their mask is not as predominant as that of the others in the guenon family. They have a pink nose with a blue-black face and ears. They possess a broad black headband reaching from ear to ear and centered with a white band over the eyes.
Whiskers are mixed gray.
The hair on the head and shoulders is a yellowish green with the back and flanks being dark, rust red. The upper side of the tail is black, with the underside being gray, as are the arms and legs. The rump is a blue-green, and is not colorful as other members of the guenon family. This feature appears to allow the young to grasp their mother's tail while she is carrying them. Generally, the tail serves as a balancing tool and is also used in non vocal communication.