I've had the problem a lot where I got no red or blue tags, and had to assume red, but I havn't seen a teammate show up with red tags. It's either a hack, or your seeing enemy and friendlies too close together... i don't know.
It's Thursday night. Put ROX into your server name and go to the ranked server, it's wide open.
That is how I bagged safrguns one night as an AT. He had no tag and with a competing tank comin at him I mistook the M1 for the other in the sight and well...he did not punish however. Funny how his name popped after I was away and could not stop with a full side shot. I keep wondering about that.