M4 Bayonet question

[EZ3]

I just bought a bayonet for my M1 carbine. It was made by Turin Army Arsenal in Italy in 1956. It looks about like any other M4 I've ever seen except for two things. The grip panels are plastic molded to look like the stacked leather washers on an M3 knife. And the blade is purple. Well, technically "plum", I guess, but I was expecting either blued or parkerized.

Is this some kind of special finish for an elite unit, a bad batch of bluing, or just some bored Italian soldier customized his gear? Does anybody know?

[nashorn]

I have seen and had a few late war German K-98 rifles with bolt parts that looked purple. I was told it's the way the blue turned out if there is a high nickel content in the steel.