Does anyone really know for sure? If they do, here's what our flies may look like to them. Compare these to the same flies I posted the other day and besides the obvious color difference, you'll see the same bright and dark areas nicely contrasted. In some ways, I prefer the subtleness of these over the colored versions. The lack of color also allows the mind to focus on the textures of the materials - natures way of letting our eyes "touch" them with our mind.
The Leadwing Coachman wet fly - see the hardness of the steel, the smooth, ridged mallard feather wing, and the soft peacock herl body? To us, its pleasing to the eye; to the trout its food....or maybe the trout also have an artistic lobe in their tiny brains just as we do when a well prepared dish is set in front of us. "That looks almost too good to eat!" Then we dig in anyway.
The October Caddis - the simple contrast of the soft fur body and thorax combined with the stiff elk hair wing over a bed of light bending antron. I'm betting the trout would take it in this colorless state just as they do in our world of rainbows.
The Peach Sulphur - something about that quill body disturbs my eye. Its too perfect, no taper or edges as might be found in a natural insect..................they work though, so who's to argue with a trout?
Kind of like taking off rose colored glasses..................