It is believed that Vishnu assumed various colours during various eras according to the nature of the living beings and their behaviour. During Satya Yuga, people were well-behaved (satvaguna) and Vishnu was white (called svetavarna) in colour. During Treta Yuga, he assumed the colour of Pavalam (emerald) and hence came to be known as Pavalavannar or Pralavannar (in Sanskrit). In Dvapara Yuga, he assumed green colour (pachai in Tamil). In the current Kali Yuga, he assumed blue tint called syamalavarna and it is believed that people will not be influenced by the form Vishnu appears. Vishnu is believed to have appeared for twin Aswini gods as Pavalavannar and hence retains the name in modern times.