All I can say is be prepared for your wife to go absolutely ape ...... horny with another guy, black, white, big dick, whatever.
Might not happen with your gal but some women, my very conservative, classy and polite wife included get so turned on with a different guy than the husband.
People are people, we all know someone we really connect with, even non sexually. And some we don't.
It's probably more than just strange dick for her, if they mesh at all she will absolutely love the sex and whatever other "fun" you guys get into.