Mona monkeys and their close relatives all have distinctive faces. The skin on their nose and around their eyes is dark gray with a possible blue or purple tint. Their muzzle is pink and covered with thin white hairs. Their face is framed with a set of white sideburns that may have traces of yellow and gray in them. The slicked back fur on top of their head is often a mix of white, gray and black fur.

The mona monkey has a colourful coat of fur with a brick-red back and white chest. The outer halves of their limbs are ebony-coloured, as are their tails. Other than their size, there is no noticeable difference between males and females.