The fact that Cole's tattoos had either changed or manifested in some way was troubling, but considering that Cole could more than take care of himself and the fact that he didn't really seem bothered by it, Castiel decided it was merely something to keep an eye on.
He tilted his head further, examining the images even further. "And what do the letters stand for?" he asked, eyes falling to the other arm.
Seeing as the only tattoos Cas was actually familiar with were meant to keep Sam and Dean from being possessed, this was something he didn't understand. Cole's did not seem to have such properties.