These monkeys are also known as Spectacled Leaf Monkeys or Spectacled Langurs. The young change to the adult colour at about 6 months of age. They usually live in the high canopy so I was lucky to see these closer than normal.
Green Monkeys, Olive Monkeys
Dusky Leaf Monkey (Trachypithecus obscurus)
Phayre's Leaf Monkey Group On Branch, Tripura State, India, 45% OFF
Dusky Leaf Monkey stock photo - Minden Pictures
Phayre's Leaf Monkey: A Future Denied
Phayre's Langur Characteristics
Zoo's first baby of the year is a colorful monkey known as a langur
Silvery lutung (Trachypithecus cristatus) - JungleDragon
13 Most Spectacular Asian Monkey Species - Textbook Travel