I saw the red also but thought the bolt may have been lying around for years since it came out of a "junk" box. If it was from an outside part that was exposed to the elements rust would be a real indicator. On a gun not sure. Stored in a box at the back of a bench after it broke, the softer areas further away from the lubricant will rust first. A lot of questions would need to be answered first and better photos would be needed to say what happened.
I was asked for an opinion on that tractor axle, the machine had 60 hours on it, but not being there when it broke left enough questions as to whether it should have been a warranty issue. If the operator side stepped the clutch when the engine was wide open would be one thing or did it break while pulling a steady load? The machine was stuck up to the axle in wet sand. The owner was not the one operating the tractor so no one questioned really knew what happened. All I could go by was the appearance of the grain structure of the steel, it looked right.
For all the comments about Krags in the reloading books there are very few cracked bolts to be seen.