"The boy's hat is black."

Translation: O chapéu do menino é preto.

[Meromorphic]

Is "negro" entirely inappropriate here? I understand that "preto" is more natural.

[Paulenrique]

That would be too strange to our ears: http://www.duolingo.com/#/comment/69864

[Shayz03]

Why do and not de?

[Paulenrique]

Chapéu de menino = boy hat

Chapéu do menino = the boy's hat