Some forms have white or buff stripes on the thighs. The upper parts are often greenish gray, but browns, grays, and intermediate shades are the common colors. The color of underparts also varies considerably. The skin of part of the face in some forms is blue or violet. Guenons are also quite variable cranially.
Cheek pouches are present.
Guenons may be characterized by having a roundish head, a slender body, long hind limbs, and a long tail. The nostrils are close together, a beard is often present, and the side whiskers are well developed. Guenons inhabit forests, woodlands, and savannahs, usually near rivers and streams. Some forms spend nearly all of their time in trees, jumping from one tree to another. The tail in young guenons is prehensile, but adults normally use the tail as a balancing organ.