I got one of those blue LED lights for christmas last year. I forgot I had it, until I was in camp this year and I took a bloody arrow and shined it at it in the dark. In the house it definitely made the blood glow. Then we went out to track the deer and in the outdoors it made the blood look black and didn't help a bit. Its still a decent flashlight but it isn't worth a Sh*t for tracking. Get a coleman latern instead (in fact get two laterns for the price of one of those blue LED flashlights, they're expensive.)