Shiva, the third god in the Hindu triumvirate, is often depicted with blue throat. This is because of this reason that he is known by the epithet “Nīlakaṇtha” meaning “blue-throated”. As per the legend, Shiva drank a deadly poison for the benefit of all living beings, and hence got his blue throat.
The incident occurred in the backdrop of the “Churning of the Cosmic Ocean” (Samudra Manthan) episode, wherein gods and demons worked together for a millennium to churn the ocean to get “Amrita” – the nectar of immortal life. Many things emerged out of the ocean during the churning process. The most dangerous among them was “Halahala” – a dreadful poison that is capable of eradicating the whole living beings.
As the deadly poison started to perish many things, gods and demons got terrified and ran to Shiva for help. Only Shiva has the power to control and digest the poison. In order to save the living beings from mass destruction, Shiva drank Halahala. Suddenly his body started turning into blue colour.
Startled at the turn of events, Goddess Parvati, Shiva’s consort, entered Lord Shiva’s throat in the form of Mahavidya and controlled the poison to his throat. This prevented the poison from spreading into other parts of the body, and his throat became blue in colour. Hence, Shiva came to be known as Neelkanth.