A grey hat hacker is a combinatin of white and black hat hacker, who are white and black hat hackers and who is more dangerous for your organization?

black hat hacker are more dangerous than white because if you follow the black it voilates the rules and it goes black list so that gray also but your site is implemented with black hat hacker your site is not going to be implement

Very simple:White hat hackers: are secuirty researchers and penetration testers

Black hat hackers: are groups or individuals who use thier hacking skills to do damage to others

Gray hat hackers:  are hackers who do both roles