What color stands out the most depends at least partly on the environment and on what we mean by "stand out." If we mean during arrow flight, then flourescent yellow/chartuese works well for me (although bright blue is a close second), like many others. If on the other hand we mean what stands out the most when trying to find an arrow on the ground, while stump shooting for example, blue works quite well, mostly because there are few blue "things" in the natural environment. Although I know this, I do not like blue fletching, however - they are just too unnatural!