I think I've read that hogs see in shades of blue.
They don't see clearly but they pickup movements really well even at long distance. They do have great sense of smell and they have smelled me out at over 200 yards in light breeze while I was sitting 18 feet up in the air. They also have great hearing. I had a sow pick up the sound of my digital camera turning on at about 75 yards and run off immediately.