Whatchya gonna do when they come for you?

Okay, so even if you commit a crime they probably still won't come for you. With all the modern technology we have and despite all of the episodes of Law and Order and CSI that indicate otherwise, only about 66 percent of all murder cases are solved.
What does this have to do with color?
Everything, if there are bodily fluids present at the scene.
If there is what appears to be blood stains visible to the human eye at the scene of a crime, it is often put through the Kastle-Meyer test to determine whether or not it is, in fact, blood. The stain is mixed with a phenolphthalein reagent and hydrogen peroxide. If it is blood, the hemoglobin will react with these chemicals to produce a deep pink color. Unfortunately there is one problem with this test...the chemicals will occasionally react similarly if they come into contact with either horseradish or potatoes. No, I am not kidding.
If blood is NOT visible at the crime scene but investigators suspect that blood was once present (before the perpetrator cleaned it up), they conduct the luminol test. Luminol is chemical sprayed directly onto the surface where blood was thought to have been. Luminol reacts with blood to produce light. It quite literally glows in the dark, and is capable of detecting blood that has been diluted up to 10,000 times. A chemical that works similar to Luminol but is preferred by some investigators is called Bluestar. Like luminol, it is sprayed onto the area where blood would have been and reacts by turning blue in color (hence the name) if blood is present. However, unlike Luminol the blue color Bluestar produces can be seen without the room being thrown into total darkness.
Another color test is used to detect the presence of semen at a crime scene. Anyone that watches television can tell you that semen flouresces under a UV light. Similar results occur when the stain is mixed with the chemical 4-Methyl Umbelliferyl Phosphate. Another way to determine if a stain is semen is to moisten filter paper with water and rub it over the suspected area. A drop or two of Sodium Alpha Naphthylphosphate and Fast Blue B solution are placed on the paper. The Acid Phosphotase in semen will react with these chemicals and turn purple in color.

All information taken from old notes acquired in my Forensics class. If you don't believe me I can bring them to class.
And I used this website: http://www.spexforensics.com/productSubclasses.asp?categoryID=16&subcategoryID=18
for info about Bluestar