Not having a Rivet I don't know if their black bleeds/rubs off or not although I guess I could contact them about any feedback/experience they might have about that... but I'd rather hear from actual consumers that own one. All I know is my Brooks never has bled and the Berthoud does. It's a darn shame about the Berthoud because, although the Brooks is comfortable, the Berthoud slightly beats it out in the comfort department. The reason (for me) that the Berthoud is a bit more comfortable is the Berthoud is pretty much flat from the nose to the back of the saddle but the Brooks has a rise where your sit bones are

bakerjw, I've read nothing but good about Rivet so your post further confirms that. You said you wear black shorts with your black Rivet so didn't know if it bled or not. Over the winter when I was breaking in the Berthoud, I had either very dark gray or black sweatpants on so didn't notice any bleeding. Then a few weeks ago, I hadn't been on my bike for a couple of days and it was raining so on the stationary bike I got (with the Berthoud on board). I was wearing light tan/beige shorts and after pedaling I had the two nicest black stripes located just off to the left and right of the "crack". My wife mused that I was getting so old I couldn't control myself anymore!