The reason brown eyes is very common is because of heredity of course. =/ Even if a woman has blue eyes, and the male has brown eyes, brown eyes will almost ALWAYS dominate blue eyes. =/ However, it is possible if the mother and father have brown eyes, then their child's eye color MAY come out blue.
However, my eyes are dark brown. See me in the light, and the pupils turn so small you'd be thinking I'm widening my eyes. They turn light brown in light. WELL DUH.
*dies*