A simple white box is a player.
Yellow means he's negative, but I can't attack him.
Red means I can attack him freely.
So:
-What does the little skull mean in the bottom right that some yellow and red highlighted peeps have?
-How do I tell the difference between PKs that are red and enemy guild members that are red?
-What does it mean when a player has a red square with a little white line in it where the skull appears?