Black Ghost? 
white people are Gwai Lo, which is Ghost Person. The name in HK is essentially the Cantonese version of The "N" word for white people with the same degree of hatred and animosity.
Lo is an offensive term roughly meaning "old punk/man". If we wanted to politically correct we'd say bak yun, which means white person. I don't think I have ever heard my family use bak yun though. It's common household vocabulary. Cantonese culture is very brash, blunt, and superstitious. Hence all the slang - especially those native to HK.
Don't forget bak gwai. White ghost/demon.
*Also a bit of background, there is no heaven in Cantonese culture. Only hell. Down. So all things death related is dark and dirty. Like really. It is described as being literally "dirty".