Their face isn't really purple - it's a very dark brown that looks purple in the right light. Around it, they have a fluffy fringe of white fur that looks a bit like a wizard's beard. Babies are born almost orange and slowly turn the dark colour of the adults.
Purple-faced langurs are leaf-eaters. Their stomachs have several chambers, like a cow's, so they can slowly digest the tough leaves that most monkeys can't manage. This means they don't have to come down to look for fruit very often - they can find lunch right above their heads.
They are amazing jumpers. A langur can leap five or six metres between trees - the length of a small car - landing exactly on a thin springy branch. They use their long tail like a steering rudder in mid-air.
Langurs live in family troops of about 10. There is usually one adult male who does most of the watching out, while the mums and aunties look after the babies. The babies spend most of the day clinging to a parent or playing wrestling games with cousins on safe branches.