After a lifetime of bowhunting a variety of animals, I can confidently say this: The brighter and whiter the light source, the "redder and better" the blood shows. Colored lights are very simply a gimmick and do not enhance our ability to discern red blood. Someone saw a potential market and the industry pounced. I've used gas lanterns, propane lanterns, halogen lights and LED lights to blood trail at night. The far-and-away winner is a very strong, very bright LED lightsource which uses a color-corrected LED. Such a light will have less bluishness and appears a bit "warmer" in its color. The average LED headlamp is good for a nice easy bloodtrail. The very strong (and increasingly pricey) handheld LED lights are superior when the trail gets tough. I invested in a Fenix TK40 over a year ago. It features a Cree Quad LED, and uses 8 AA batteries at once to emit over 750 lumens of light. I can clearly see a deer at 100 yards and a deer's eyes at 1/4 mile with this light. I gave over $150 for it, but I also rely on it for home defense. One blast to the eyes and you're blind for over a minute. Best light I've ever held in my hands.