His throat is blue for the reason that he experienced drunk poison, which erupted from the sea through Samudra Manthan (churning on the ocean). Consequently, he usually wears a cobra all-around his neck to mitigate the effects in the poison. The title Neelkantha (A single who has a blue throat) https://travisbbxqj.oblogation.com/28799043/a-review-of-shiv