What color can bees see that humans can not see? Why is this important?

UV, because bees can locate the sun even through the clouds on an overcast day and use that for navigation. Also, because flowers that need bees to pollinate them use UV colors to attract those bees. Sometimes the UV color is shows on the flowers in markings that point the way to the nectar and pollen sources in patterns that suggest the runway light patterns we find in modern airports.