From what I understand, this blue color is caused by a protein. The blue color is in the mucus of the fish. You can actually scrape some of it off and put it in clear water and you'll see the blue pigment.
Quotes about mucus (6 Quotes)
Let him not step intentionally on things used for cleansing the body, on water used for a bath, on urine or ordure, on blood, on mucus, and on anything spat out or vomited.
With each meal, when edible substances find their way into the oral cavity, thick and viscous saliva containing much mucus flows out of these glands.
The reason you cough is that your body is trying to mobilize mucus and break the secretions up -- your virus load. Fever, too, is part of the body's way of trying to kill viruses. They don't tolerate a high temperature.
What parents usually hear are the random snorts and sniffles of air passing through mucus and secretions in the nose and throat.
It's gross. I don't know what it says about me or the people in the business. But mucus is the underlying problem. People talk about the symptoms and relief, but we're the only ones talking about the underlying causes of the symptoms.