Why Krishna's Skin Is Portrayed Blue Or Black In Art
The Isha Foundation notes that Krishna, along with other Hindu gods, including Shiva and Rama, is often depicted with blue skin. It's not that their actual skin is blue, but rather their auras, which then makes their skin merely appear blue. Writer Sadhguru defines an aura as "a certain field of energy that is around every substance" and calls blue "the basis of all-inclusiveness." He notes that because of his blue aura, Krishna was incredibly appealing and attractive to people, noting that Poothana was actually sent to kill him when he was a baby but instead fell in love with him, all because of the blue energy surrounding him. Sadhguru goes on to explain that those with blue auras are seen as "superhuman" by other people. The color blue indicates someone with massive dynamism who may be at the highest possible point in their evolution but still chooses to be active within the living world.
Slightly Blue reports that there is an actual scientific reason that some people have blue skin. Methemoglobinemia is a skin condition in which hemoglobin within the blood can't distribute oxygen throughout the body, and the lack of oxygen leads to the skin developing a blue tint. Skin can also turn blue when people are exposed to various substances, including nitrates and uranium; in 2009, there was reportedly a slew of babies in Punjab, India whose skin turned blue in response to an increase in the use of chemical fertilizers. This was referred to as Blue Baby Syndrome, and similar issues were seen in Bulgaria and Romania.