The  room or passageway I was walking into could mean the path or choice I took. It is still a mystery as who the one with the white robe was but I think it is one of pureness. The blood-red card I know refers to the emotions I am currently feeling and the anger to the sins of Man. Likewise I could be symbolizing His people who are my brothers. He was saying that we are that red card but if we choose to take the right path and enter that room, he will be there to wash the blood away and make us as white as his own robe.