Deer have reduced color perception compared to us, but they aren't totally color blind. They can percieve blue, violet, yellow, and green well, and orange to a lesser degree. Once the light shifts toward the red end of the spectrum their accuity drops quite a bit and they begin to see in grey scale. This was taken from a university study that somebody posted a few years ago, it illustrates approximately how game animals see light:



Note how well deer see into the ultraviolet spectrum, so check your hunting gear with a blacklight to make sure you aren't "glowing" when they look your way. I checked mine recently, my brand new snow camo and a blaze camo parka both glowed rather brightly, my other clothing didn't other than a few tiny specks of lint they picked up from the dryer. Applying UV killer will negate the glow, using a detergent like Sportwash that doesn't have UV brighteners will help keep them dim.