Grey Hat (or Gray Hat): Since the color gray is between black and white,logically Grey Hat SEO sounds like a label for the middle ground.

But it’s not.Because White is pure white and grey is a shade of black, we have confusion.

Some say Grey Hat is NOT White Hat and is just a shade of Black Hat.

So let’s step away from the coor wheel and define Grey Hat as the practice of tactics/techniques which remain ill-defined by all that published material coming out of Google, and for which reasonable people (not White Hat SEOs, mind you, but “reasonable people”) could disagree on how the tactics support or contrast with the “spirit” of Google’s published guidelines.