Ballpoint pen can bleed through paint amazingly too; at least one of my buildings has some marks on an inside wall from some quick markup I did before cutting, using a ballpoint instead of a pencil. Damn thing is still visible after at least four or five coats of paint, too!
The ice board is coming together amazingly, though, and as people have already said, black at least is just extra depth and cracks in the ice. Blue or red ink might have been a bit harder to explain away.