Blue monkeys are small and arboreal. White whiskers are well developed in males.
Males are larger than females.
The upper parts of the body are gray and the limbs are darker in appearance. Breeding occurs throughout the year. There are two facial expressions performed by the female before and during copulation. Presenting, this tells the male that the female is ready to copulate. Pouting, this is a display performed during copulation, as the female looks over her shoulder.