I am sorry that you were sucked in by this lie.
That isn't blood you are looking at, it's a forensic test substance that was sprayed on the walls to look for blood. In about 30 seconds, it will oxidize and create the pink color you are seeing even if there is no blood.
The defendants in this case were smeared in the press long before the trail even started. The bloody bathroom fallacy is just one of many examples.
This video includes footage taken the day after the murder, showing what the bathroom looked like on the morning after the crime.
Amanda Knox - Bathroom Fallacy - What Amanda Really Saw - YouTube