“黑” means “black,” but also can mean “sinister,” and “化” means “to turn into.” This term, originating from Japanese anime “Fate/Stay Night,” refers to scenarios where a character who started out as kind and innocent gradually becomes cruel and evil, often after undergoing traumatic experiences.
Nǐ hái zài zhuī nàge kēhuànjù ma？
Are you still a fan of that sci-fi TV series?
Bù zhuī le，yīnwèi wǒ xǐhuān de nǚzhǔ hēihuà le。
Nope. I stopped watching it because the heroine I liked has turned into an evil person.