User blog:Bioniclepluslotr/Blue crosshairs

In the zombies loading menu of Black Ops, one of the hints mentions "what do blue crosshairs mean?" I know that the pack a punch ballistic knife has blue crosshairs when aimed at a downed player, but are there other reasons? I remember this one gamewinning kill where a teammate got the kill and I walked right in front of his crosshairs at the end, and they were blue on my screen. Does this show up on everyone eldest screen, or just mine because it was me? Has anyone else experienced blue crosshairs?