FWIW - Here's a listing that shows which states and provinces require hunters to wear orange:
http://www.ihea.com/hunter-education/hunter-orange-requirements.phpI think the problem with all colors other than orange, including the reds, blues, neons, yellows, whites and even pink (Yuk!) is that they blend in (at least as to the human eye) with fungi, bark, colonies of lichens, mold, moss (that can have different shades of green & red in my area) and other things that grow on or around trees.
Even when the trees' leaves are turning color in the fall, the human eye tends to be able to distinguish the color orange from the leaves.
It's been my experience that colors appear differently in the forest than in direct sunlight. I think this is due to the impact (filtering) of the canopy and the color distortion caused by the ecosystem of the forest itself.
Everyday in a forest is like a heavily overcast day on the beach. Orange and lime green are the only two colors that don't turn gray to the human eye in low light conditions. If you've ever taken a black and white picture of a rainbow you may have noticed that it's the most prominent colors in the visibility spectrum that are no-shows in b&w.
In the timber management business (where timber landowners frequently paint exacting marks on trees surrounding the perimeter boundaries of tracts of woodland to discourage trespass and reduce adversarial possession) the best paint colors to use from a visibility standpoint are either orange or sometimes lime green. However, large timber companies generally use a uniform (companywide) color of paint scheme in their boundary line marking (
e.g. yellow, dark blue, white), without much regard to visibility. It's kind of neat though to know who owns land simply by looking at the boundary line paint as you cross from one tract to the next.
Here's some typical remarks about colors found in forest management literature: "Red is not a preferred color. As it fades, it is difficult to see. Also, red is difficult to most people who are color blind." In any case, I still use a lot of red paracord because I like the color. Recently I found that red is one of the few colors that's available in 400 yard rolls (and sometimes in 700 yard rolls) of recently manufactured Certified C-5040.