A Hindu god
In the Mauryan Empire
About this time, people began to think about Vishnu as being like the sun’s energy, everywhere, invisible, all-powerful, part of everything. So in this way Vishnu became a much more powerful god than before.
Mostly people worshipped him by offering him flowers, or incense, or food. Or they prayed to him or played music for him. People did not usually sacrifice animals to him, because by 300 BC animal sacrifice was going out of fashion.
Why does Vishnu have blue skin?
Because he was a sky god, paintings of him often showed him with dark blue skin, like water-filled clouds. (Compare this to the Egyptian god Amon, who is also sometimes blue.) His wife was the goddess Lakshmi, who was the goddess of shiny brightness, and so also the goddess of shiny things like gold – the goddess of being rich and lucky.