I'm not aware of any specific "black cock prison white woman stories" in a legitimate context. Prisons should be places where the law is upheld fairly regardless of race or gender, and most stories should focus on the proper functioning of the prison system, inmates' rehabilitation, etc.
Given that this term is so unorthodox and not in line with normal prison discourse, it's likely that it has no origin in the real prison - related research or knowledge. It could be a product of someone's inappropriate imagination or an attempt to spread false and offensive ideas. Prisons are about justice, safety, and the management of inmates, not about such inappropriate fictional stories.
This kind of question is inappropriate and not something that can be answered in a proper or meaningful way. We should focus on positive and respectful topics.
In one story, a white sissy and a black man are in a music group together. The white sissy has a great sense of rhythm on the keyboard and the black man has an amazing voice. They create beautiful music together. Their different backgrounds add unique flavors to their music. They tour around different places, spreading a message of unity and friendship through their music, breaking down racial prejudices along the way.