Pavalavannam

1. During Krita Yuga, people were well-behaved (satvaguna) and Vishnu was white (called svetavarna) in colour. 
2. During Tretayuga, he assumed the colour of Pavalam (emerald) and hence came to be known as Pavalavannar or Pralavannar (in Sanskrit). 
3. In Dvapara Yuga, he assumed green colour (pachai in Tamil). 
4. In the current Kali Yuga, he assumed blue tint called syamalavarna 

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