My expierences have taught me that blue light may make blood shine and green light makes blood look like tar, but nothing beats the old fashion latern, or regular flashlight not a LED one, it's kind of unatural for me when the sun is yellow and a led light is white to look for blood, back a few years ago my cop buddy brought some of this type of spray they use in detective work to find blood on a track job, if you made a questionable hit on a deer your going to need gallons of the stuff to find blood , you have to spray everthing in sight. Does it work, sure it does but it can get real expensive real quick, especially if you don't find the deer. It makes the blood turn blue, depending on what type you use. My opinion, use a regular latern or flashlight.