Actually, it doesnt matter what color the bear's skin is. We see the color of something because it absorbs a certain wavelength of light in the visible region and reflects the rest of the light back, therefore causing us to see the color of the reflected light. Simply put, a dandelion would absorb blue light, and reflect back the yellow light. Because the polar bear's fur is clear, it therefore has nothing to absorb light and reflects back all colors of light, which means we see white!