Well, I learned later on that it wasn't close to her first bbc, but she first brought it up. When we first started out, we hooked up with 10 or so couples on AFF, back in the mid-2000's when it was a site with real people. During every single encounter, every single time, it was obvious that the guy just wanted to watch me fuck his wife, and I just wanted to watch him fuck mine.
Eventually, I brought this up to her (it must have taken me few strong drinks), and suggested that it would be way easier to just invite guys over to fuck her, than dealing with trying to click with a whole couple, where neither guy was all that interested in fucking the others wife. Dealing with couples really is a pain in the ass, and considering (in our experience) almost every husband was really just a cuckold that hadn't come to terms with that fact, ultimately resulting in two unfulfilled wives, it just made more sense to invite the cream-of-the-crop single guys over to fuck her.
Anyways, it was at that the end of that conversation that she said she was fine with fucking other guys, but if she was going to do it she wanted me to find black men. Because she was 'curious' and 'had never fucked a black man.' LOL. Like I said, I later learned that was total bullshit, but that's how she openly started fucking black men.
-Bonus content: I actually have pics from her first encounter[that I knew about]. As luck would have it, he ended up being huge, and she came out of the bedroom afterwards with her own cum running down her legs. You might have seen these pics before, but that's because I first started posting them on swinger sites in 2005 and they've been reposted multiple times.