Why are inedible poultry parts dyed blue-purple?

In the context of poultry processing, inedible parts are dyed a blue-purple color to ensure food safety and regulatory compliance.

During the evisceration and inspection process, government or plant inspectors examine poultry carcasses to ensure they meet health standards. Any parts or entire birds that are rejected by the inspector are placed into containers specifically marked as "inedibles." Under the supervision of the inspector, these rejected materials are dyed blue-purple to provide a clear visual distinction, thereby preventing them from being accidentally mixed with edible poultry products.1