Often the rabbits get startled when I enter the kitchen and only when I greet them do they know who I am. This is because rabbits have quite bad vision, and usually tell what things are by their smell, noise and shape. They have a very narrow area where they can focus on and judge distance well even though they can see almost 360degrees. They have a 10degree blind spot in front of their noses. Not to freak out a dozing Pixel, I usually talk when I enter the kitchen so he knows its me, and continue to talk as I bend down to pat him.  Nybble seems more trusting of anything that moves and doesn't generally freak out!

Rabbits only see in blue and green, and have grainy vision. I'm not an expert in vision, so I don't know if this means that everything red becomes a grey (sort of like colour blindness) or a mixture of blues and greens? I would think it would be grey; their world consisting of white, black, blue, green and various blue-greeny greys. I tried to emulate this with a photo. Any better attempts welcome!

The original photo:

With red completely gone:

And with red turned to grey:

References:
http://www.wisconsinhrs.org/Articles/What%20Do%20Rabbits%20See.htm
http://www.threelittleladiesrabbitry.com/rabbitvision.php