Duncraft makes decals to put on your windows to keep birds from striking. They are called "Save-the Birds," and they work by marking the window glass in near-UV "colors." We routinely have birds taking off from the birdfeeder and crashing into the windows usually when they are scared by other birds.
I like the idea of this since birds see different colors than people. Like everyone, I wonder how birds see differently than I do.
People have three color receptors in the eye, but birds have four, including one in the near UV. If one puts a UV absorber in a clear object, birds can see it, but people see nothing.
In regard to a product review, I don't recommend the Save-the-Birds decals by Duncraft because they are still to visible to me. I think they are distracting. I don't know how well they block birds, but they are not as transparent as I hoped they would be.
As discussed, people can only imagine what 4-color vision looks like, although we could use a UV camera to guess.
More interesting is introducing this fourth color receptor into people by genetic engineering. We know that mammalian ancestors had four receptors, and the our line lost them somewhere along the way -- probably during a nocturnal phase of development. Anyway, reintroducing the gene into the eye should induce Super color vision -- though one might have to be very young to have it work. That is the brain would need to rewire itself to perceive it.