One Bearing - Black Color

Okay, my brother bought a YYF One not long ago. He has been really enjoying it with whatever responsive bearing there is on it.

Well, now the bearing is turning black and I have no clue why. ??? I have never lubed it or cleaned it. Does that mean I need to?

If so, with what?

Nothing to worry about.

If you want to clean it, use whatever you want to clean it: acetone is my choice. I notice most older steel bearings do this. I have quite a few like this and none are giving me any issues or cause for concern.

It’s just oxidization from what I know