Deer see the world very differently than humans.
Deer have a much higher density of rods in their eyes than humans. This means they are better at detecting motion and they have better night vision. Deer also do not see longer wavelength light well so reds and oranges a appear much less bright to deer. Conversely deer see blue much better than humans which means you should never wear blue jeans while hunting which is the opposite of our eyes.
Watch the video from whitetail 101 to get a primer on deer vision.