I change a lot of spinner cones.... sigh.
What most likely happened here is that they borrowed one from another carrier, or as someone stated above, one engine is leased.
I believe Swiss PW4000's used the white spinners... But LX
was not alone in that.
The other one isn't unpainted, it's simply black.
Now, paint is NOT a requirement; when the paint falls off (which it invariably does), you can keep the spinner flying without it. You simply have to do a visual check for corrosion. But, that said, they all have paint when new or overhauled.