Want to know what color your baby’s eyes will be? The fact is that there is no sure way to predict. It’s complicated. Even if you and your mate have the same eye color, your baby may have a different eye color. Eye color is determined by the amount of pigment you have in the colored part of your eye, your iris. Lots of pigment makes brown eyes. Less pigment makes blue eyes. Somewhere between the two are hazel and green eyes. 
Eye color is not just hard to predict, it is a moving target. About 100 years ago, half of all Americans had blue eyes. Now only about one in six Americans have blue eyes. Blue eyes are getting rare because genetically, brown eyes trump blue. There are about 7.5 billion people in the world and only about eight percent of them have blue eyes. Only in Europe and America are blue eyes common. As more and more brown-eyed people come to America, and more and more Americans mate with them, baby blues are becoming less common. 
The Story of Eye Color
If you lived about 10,000 years ago, you would not be wondering what color eyes your baby would have. Everybody had brown eyes, and so would your baby. That all changed when a single human – probably in Europe – developed a genetic mutation in a gene called OCA2. This gene controls the amount of pigment humans make in the iris. [2,3]
From that one human, a population of blue-eyed people developed. Blue eyes do not give a person any survival advantage. They are not healthier or better. They are just a genetic variation like hair color, freckles, or baldness. But early humans must have had a thing for blue eyes because they mated with each other a lot. Over time, blue eyes became common in Europe. Since America was mainly colonized by Europeans, blue eyes became common here. 
Why Genes Can’t Precisely Predict Eye Color
If the OCA2 gene were the only eye color gene, predicting eye color would be easy. If both parents had blue eyes, baby’s eyes would be blue. If one parent had blue eyes and one parent had brown, baby’s eyes would be brown, because brown is a dominant gene. But there are about 10 genes that contribute to eye color. This results in a less predictable mix of eye color possibilities, especially if you throw in hazel and green. [2,4] Here are the basics for brown and blue: 
- If you and your spouse have blue eyes, your child will very likely have blue eyes.
- If you both have brown eyes your child will likely brown eyes.
- If there are grandparents with blue eyes, odds for blue go higher.
- If you and your spouse have different color eyes, the odds are even for blue or brown.
If you want to really get into eye color, you can find eye color prediction tools online. Just search for “predict baby’s eye color.” But remember, the best these tools can do is give you a prediction.
Baby’s Eye Color Changes Over Time
Finally, don’t be fooled by your baby’s eye color at birth. The cells in the iris take time to produce pigment. Pigment production is stimulated by light. Since your baby just spent nine months in the dark. His or her eyes may look blue for the first six months or a bit longer before that assume their final color.