My wife dated a black guy before we met when she was in with work and travel in the US(we're not from US in our country there are very few black guys).
She told me that he had a huge cock and she would suck it all day long. I know she has a thing for black guys.
However, convincing her into cuckold isn't an easy task. I still want to keep the marriage and she's not so eager about it.
Our only experience was on the summertime in Greece where a young black waiter our age and my wife exchanged some smiles and when we left he asked why we are leaving so early. Than he offered us some pot to smoke on the beach and next thing I know was in our room my wife sucked his cock and then he fucked her several times that he left. I was so horny and I fucked her also but she fell asleep. No other experiences so far. It kinda became a taboo although we do bring this up once in a while like me teasing her about her loving black cocks.