RE: Deer cannot see orange.
The number of Rods and Cones in the eyes of all animals, including humans, determines what or how that animal sees. Deer are a nocturnal animal which requires specialized sight, color is not part of this specialty. For myself, Ive had deer under ten feet from me on the ground while wearing orange and they had no clue I was there and I was in plain sight. As for needing more than one sense to spook? Thats a tough call, I tend to believe scent maybe the only single scense that may do it alone. Ive had them see me and not spook, Ive had them hear me and not spook, but every time they have smelled me they spooked.