Is it normal for this saddle to turn black after it's broken in? I've had it for about one year now and it's super comfortable, but it's turning black, especially around the rivets. I never ride it in the rain, so is it possibly my spandex dye running? It does get a bit wet after each ride due to sweat. Any worries or is it normal?

I have one and it's doing the same thing. I think that's just what happens. Sweat probably has the most to do with it.

It's Possible that if you use it more than once a day for more than an hour at a time that your sweat is keeping the surface of the leather wet. Try using another bike and let the saddle dry out. Afterward give it a good over night coat of Proofide. What it could also be is that you are over using Proofide now that the seat is Broken in, no more than once a season should the saddle be treated after break in.

Just some thoughts.