I'm not sure of your age, but as one grows older, the skin under the eyes gets progressively thinner, making the veins under the skin more "visible." Thus the oh-so-attractive tint. If you're relatively young, there might be another cause. Dark circles are also common in people of Mediterranean descent and those with allergies.
They can be lasered away, but a less-drastic option is a good coverup cream. Physicians Formula makes a good, inexpensive one.