The toughest human to hide from in the bush is a trained, but color vision deficient person. Their mind has subconsciously learned to ignore color (more or less), and is looking for your movement (or the movement of your shadow), your lack of movement (Gee sarge, why is that one 6 foot patch of grass NOT blowing in the wind when all else is?), and shape.

Oddly enough, the first MEPS physical I took showed I am color blind (OH BOY AM I TOO!). When I had to go back just prior to leaving for basic though, they marked me as perfect in the vision area. I didn't argue, and got the job I originally wanted.

Supposedly, the color vision issue deals with red-light readable maps at night. I was told I would only see a blank sheet of paper. Never had a dime's worth of trouble, and was usually the one to go out and find lost Navy doctors or Signal Corps 2LT's.