Slit Flange
When a man and/or a woman has a color of beard that differs from the color of the hair on top of their head, and when their pubes are a different color than their beard and hair. They are not a doupo, for a doupo's pubes could be the same color as their beard or hair. Whereas a doupo usually brings good luck, a slit flange tends to bring bad luck. They are very rare and even if you see one, it's near impossible to know if they are a true slit flange, because they are probably wearing pants. If possible they are best to avoid.
"That man over there looks like he could be a slit flange. I can't tell though, because I can't see his pubes."
"I wouldn't even look at him, just in case he is."