Why is Krishna blue?

Lord Krishna has been depicted as a baby stealing butter and a charming boy with a flute in his hand and a peacock feather on his head. In all these depictions, there’s one common link though: the blue colour of his skin.

There are different theories to add on why Lord Krishna is bluish in Colour.

One belief is that when Demon Putna tried to kill baby Krishna by her poisoned milk, Krishna didn’t die, instead, his skin became blue.

Another belief is when Krishna was defeating the Five-headed snake Kaliya, some of his poison affected him and turned his colour blue.

The same theory is floated to explain blue throat (Neelkanth) of Lord Shiva, who is believed to have drunk the poison to save the world from destruction at the time of Samudra Manthan.
Etymologically speaking, the Sanskrit word ‘Krishna’ means black or dark. At times, it is also translated as “all attractive”.

Sanatana Dharma (Hindu religion) believes in symbolisms and the blue colour is a symbol of the infinite and the immeasurable.
Another theory refers to Vishnu implanting two hairs, one black and the other white in Devaki's womb which miraculously got transferred to Rohini's and as a result, from the black hair Krishna tool birth, with a dark skin, and from the white hair his brother Balarama.
Some are of the opinion that the bluish tinge in Lord Krishna’s skin is not the colour of the material body but the eternal spiritual body of the Lord that emits a blue aura.

According to Bhagavad Gita, the blissful form of Lord Krishna is visible only to pure devotees. He may have bewildered the non-devotees, but those who offered pure devotional service to Him had always seen Him in his blue blissful form.
Another belief is that Lord Vishnu, because of his association with water, is depicted blue; therefore, all his incarnations including Krishna, are shown as such. In Sanatana Dharma, those who have the depth of character and the capacity to fight evil are depicted as blue skinned.
The theory of the blue colouring of Krishna goes to the fact that the Creator has given the maximum of blue to nature i.e. the sky, the oceans, the rivers and lakes. The deity who has the qualities of bravery, manliness, determination, the ability to deal with difficult situations, of stable mind and depth of character is represented as blue coloured.
The blue colour of Lord Krishna embodies the vastness of his character... the depth of his vision... the unfailing timeliness of his deeds.

The blue colour of Lord Krishna encompasses the whole cosmos. In spite of millions of glowing stars in the sky, universe or galaxy is blackish i.e beyond our vision. It appears blue in the day due to sun rays but in fact, it is black and infinite. Imagine how vast our universe is So Krishna’s colour is like the infinite universe.