If you are worried about it Cold Blue will work. However it is an Express (not knocking them I have some and have owned even more), and they will happen. I clean them with CLP, and what doesn't come out gets black magic marker. Not very technical, but they are working guns, used mostly for waterfowling-about the worst sport on shotguns. If yours isn't going to get worked that hard, the bluing will work, but won't match perfectly in my experience.