How about all of the blood you leave splattered around fairly frequently? Especially after you've run another player or one of the enemy over or if you beat them down or start beating on the corpses, weapons like the Energy Sword and Gravity Hammer left plenty of blood as well. Explosions sometimes did as well. All the blood was [i]especially[/i] apparent in CE, though it got slightly less noticeable as the series went on.

Now that you mention it I remember painting a hallway purple will Elite blood in the original CE.