The University of Delaware suggests that it is possible for two green-eyed parents to have a child with brown eyes. As Science Daily reports, the polygenic nature of eye color genetics is the reason why almost any parent-child combination of eye colors can occur.
However, Discover magazine reports that darker colors are more dominant and are more likely to win through. As Wikipedia explains, this means that if both parents have brown eyes, there is an increased probability of having a brown-eyed child. Two green-eyed parents could have a brown-, green- or even blue-eyed child. Eye color can also be affected by changing levels of melanin with time, and a blue-eyed newborn could become a brown-eyed child, according to the University of Delaware.