Eye color is determined by three governing factors:
- The parents eye colors
- Whether the parents are homozygous or heterozygous for that color
- If the parents genes for eye colors are dominant or recessive
In general, inheritance of eye color is considered "polygenic." That means that parent's genes usually (but not always) determine the baby's eye color.
Parents can carry both of the same gene (homozygous), or, what is more likely, they carry a more dominant gene, and another less dominant gene (heterozygous). It's usually impossible to determine whether a parent is heterozygous or homozygous. Brown and maybe green are considered dominant. But even two brown eyed individuals can make a blue-eyed baby, because this does not always completely follow the rules (it's therefore called "polygenic").