Warning - contains head-canon...
Grey
Grey's mark was a shield for him, a mask to clothe him when nothing else remained. The deep blue ink coiled around the edges of an ice-caused scar. He had thought that by covering the shame of the wound caused by the white-haired boy who had once been his best friend, he could hide it from the rest of the world.
Unfortunately, his legacy worked against him, and when the others eventually found out, he expected laughs, concern, maybe even anger (though directed at who he couldn't decide).
What he didn't expect was Cana placing a gentle hand against the mark and saying "You know, it would have healed much better if you hadn't tried to hide it..."