Our peripheral vision is black and white because it is a part of vision that occurs outside of the center area of the retina, which has a high dense photo receptors and it takes advantage of the rod cells which are insensitive to color in our retina. Therefore, our peripheral vision perceive less color and is less sharp.
Well, it seems that you have little knowledge about what peripheral vision is all about. As you can see, our vision could be seen as two parts, central vision , and peripheral vision . Central vision is what you can see most clearly in front of you, peripheral vision means what you can see less clearly in front of your eyes, areas around your eyelids. So, it becomes clear that peripheral vision is of course not black and white.