Sorry about the quoting. I should've scrolled back up to find the exact wording.
About the criteria ... I kinda gathered from your post that, even though we don't know the specifics, it's all about the grade it's in (as in, if it grades at a certain point or lower, it gets a blue). Is that correct? I was thinking that that was probably the case, but there was a possibility of it being something else ... like the size of the sig or something.
Am I correct in assuming the grader makes his/her decision on label color based on the grade, but nobody here knows what that grade is? And in this particular case, the comic that received a blue label, would've received a lower grade than the rest if they were all sigless. <-- yeah, I just made that word up