not sure what you are asking about please give us a model or upc of the item you are asking about if you are asking about the Blue blue is an electrochemical conversion coating process in which steel is partially protected against rust, and is named after the blue-black appearance of the resulting protective finish

Larry, "Blue" is just the metals protective coating like these other examples: Cerakote, Parkerized, Stainless etc.

Larry, The term 'blue' refers to the protective coating on your firearm. Bluing is a chemical/natural process to protect/weatherproof your gun. There are many different types of treatments to protect your metal on your firearm. It will still take maintenance. Keep it clean and dry when your done using it and put some light gun oil or water repellent lube on your gun when storing.