Commenters pointed out that it looked like a case of green muscle disease, which happens from disruptions in the blood supply to the bird’s pectoral — or breast — muscles.
Commercially reared poultry tend to have far larger breast muscles than they would normally, which means the blood supply to the muscles is inadequate.
Despite the lack of safety issues associated with the color, consumers are put off by the defect. One member succinctly stated on Reddit, “Oh my, I gagged. Not normal.”