I remember when I first started taking flying lessons. I was amazed by how much bright blues stuck out (think of those cheap plastic tarps). Earth tones all around with big blue dots everywhere (the dots were swimming pool liners). It just seemed to be an unnatural color.
The "best" color depends on where and "when" you are. Those bright oranges and yellows wouldn't be very good in the fall, when the leaves start to change & fall (I live in east PA).
We have a few guys in my motorcycle "gang" that line the rear of their bikes with alternating diagonal stripes of different colors & reflectivity. Then it's not just color but pattern too (diagonal stripes seem to scream 'man-made'). I'd think adding reflective strips would also help, especially in the dark. Does anyone make cordage in blaze orange and/or bright blue, with reflective white stripes thrown in?? They'd have to be changed every now and then when they get dirty.