I would agree, to a point, that bright fletches are usually no problem while hunting. However, I would point out that most game animals do have a flight response to a light color. The tail end of sheep, mulies, elk, antelope and (of course) whitetails are a light color. There are probably two reasons for this - one is the herding response of many of these animals. A light colored behind makes it easier for the members of the group to follow each other - particularly in lower light conditions - which helps a group of animals to keep in touch visually with each other.
A light colored behind flashing also quickly catches the attention of other animals in the area, which can trigger a flight response. With whitetails the flash of the tail can be an altruistic response to danger, which alerts any other deer in the area. The same applies, although to a lesser degree, to antelope (probably mulie, sheep and elk too), in terms of the flaring of the white rump hair to signify danger. A flashing light colored rump, or even a light colored rump moving quickly, is quite visible to other animals and can be a warning of possible danger.
I have hunted with partners that have used all white fletch, and the movement of that white fletch (when we are separated) is the way I can most often pick them up in the woods. Makes me think animals can see that too and, since white can be the color of danger in the woods for many ungulates, it might be best to stay away from all white fletch. This is by no means definitive, but thought I would bring this up as something to consider.
