Final answer:
True, mandrills are Old World Monkeys with colorful facial markings and males have blue scrotums used for communication, reflecting the sexual dimorphism and communication systems of Old World monkeys.
Step-by-step explanation:
Mandrills are indeed forest dwelling Old World Monkeys known for their distinctive colorful facial markings. The statement that male mandrills have blue scrotums that are used for communicating with one another is true. The bright coloration of the scrotum can be associated with social hierarchy and is a part of their complex communication system, which includes visual signals. Old World monkeys, such as mandrills, generally exhibit significant sexual dimorphism, with males being considerably larger than females, which contrasts with the sex size equality observed in many New World monkey species such as marmosets and tamarins. Mandrills, therefore, reflect the typical tendencies of Old World monkeys in terms of physical and social attributes.