For many years "Studies" showed deer could only see black and white. What HS. I had a doe(Not a yearling)keep coming closer and closer stomping her foot when I was sitting behind a log. I thought she was looking at me. I had on a face net and she could not see my glasses. I had my quiver propped against the tree I leaning against, and that is what she was concentrated on. I had very bright dyed feathers on the arrows and she saw them. There were other deer milling about behind her and I knew it would end badly, so when she was just about in my face, I threw a handful of dirt at her. It was worth it to see it. This was long before the UV nonsense. Deer are not stupid, they learn (If they live long enough). The whole tree stand craze started because "Deer never look up". I have news for you, when they feel something is out of sorts, they start checking the trees. I have seen it.