MLM I believe that it depends on the persons who are making the love connection. We all bring baggage to a relationship (some bring more than others).
Example some white women might pick a black man because she was abused by white guys in her previous relationships. Some black women have done the reverse and if you interviewed both would say that it is because they are treated with respect.
I am still trying to figure out one of my wife's friends who was married and had four children. She found out that her husband was a cheat and she left him and is now in a lesbian realtionship of over 5 years. She says that she is still attracted to men but she finds that her companion fulfills her emotional needs and respects her. Am thinking that she was bi before te husband cheating thing.
So my point is that we are sometimes, for good or bad motivated to do things outside of the norm for various emotional reasons and race plays a smaller part, in fact I would venture that religion and cultural upbringing can have a greater influence on a person's choice of lover.