This is a folk belief that was told to the informant by a Jamaican. According to this belief, if a Jamaican man has a white belly button, then he is lucky.
A white belly button is probably unusual, thus could be considered lucky. There could be a lot of cultural historical stereotypes that play into the tradition: if one was pale in Jamaica, chances are they were not slaves and were therefore fortunate. My informant shrugged about it, and said that it held true for the person who told her that was the case, as it applied to him and he was very fortunate in wealth and dates. It’s possible that he simply invented it to impress her, or that perhaps through his belief in his luck his life outlook changed and he took more risks, and the successful ones reinforced this belief.