At birth, babies often have bright eyes—sapphire blue in babies with light skin and gray in those with darker skin—that captivate us. Even though you might wish they would keep this color, it’s very likely to change to another shade. What determines eye color? Can you predict your baby’s eye color? At what age does it become permanent? Find all the answers to your questions in this article.

What determines eye color?

A baby’s eyes develop in utero, as early as 18 days, when two tiny black dots become visible. Then, the eyelids form during the second month of pregnancy, but it isn’t until the seventh month that the baby can open them for the first time. What about the final color? Although it isn’t yet visible at birth, it’s a genetic inheritance that occurs at the chromosome level—specifically on chromosome 15!

A brief biology lesson: a baby is a combination of their mom’s and dad’s genes. Your child inherits your genes, and each gene has two alleles that carry a color. One allele is dominant, and the other is recessive, meaning it is masked by the dominant one. The order of color dominance is always the same: brown overrides green, which overrides blue; consequently, brown also dominates blue. Thus, a baby inherits four allele colors at random from the eight available in the genetic heritage of their parents . If you and your partner have blue eyes, it’s very likely that your child will inherit them. However, nothing is ever certain with genetics, which can sometimes be surprising—especially since it also takes into account the genes of the grandparents. Your child’s eye color can therefore be a surprise, as they may have inherited their features.

Why are babies' eyes blue at birth?

Newborns with light skin generally come into the world with grayish-blue eyes, because the outer layer of the iris does not yet produce enough melanin to color it. By the way, did you know that melanin is a biological pigment that determines the color of the eyes, skin, and hair? The blue color of newborns’ eyes corresponds to the color of the deeper layer of the iris, visible through transparency.

Over the months, light stimulates melanin production, gradually pigmenting the iris. The higher the concentration, the more likely it is that the baby’s eyes will be dark; conversely, if it is low, the probability of light eyes is higher. For this reason, it’s best to wait a few months before determining the final eye color of your little adventurer.

In dark-skinned newborns of African or Asian origin, the same phenomenon is observed. They are usually born with gray or light brown eyes that darken over time.

At what age does eye color become permanent?

In the first months, it’s normal to observe a evolution of a baby’s eye color before it takes on its final shade. For example, eyes can change from blue to green before finally becoming brown. It is estimated that around two or three months, it’s possible to get an initial impression of the final eye color for dark shades. As for light eyes, you’ll need to be a bit more patient. Indeed, if the blue color persists at six months, you may have to wait until nine or even ten months of age to get a clearer idea of the final eye color. At this age, the color can be considered final; however, its shades can still vary until the child is eighteen months old.

Can we predict the baby's eye color?

As you can see, a baby’s eye color is a matter of genetics, melanin, and also chance. Although genetics can sometimes be unpredictable, depending on the parents’ eye color, the following predictions can be made:

• You and your partner have brown eyes : in 75% of cases, your little one will have brown eyes. Their eyes can also turn green and, in rarer cases, retain their blue color. The reason? An allele inherited from one of their grandparents with blue eyes.

• One of you has green eyes, the other has brown eyes. : in this case, it is more difficult to predict the baby’s eye color. Although brown has a clear advantage, anything is still possible.

• One of you has blue eyes, the other has brown eyes : ball in the center! In this case, your little adventurer will have a 50% chance of having blue eyes or brown eyes.

• You and your partner have green eyes. : in the vast majority of cases, your little one will inherit your green eyes; however, it is also possible that they are blue or, more rarely, brown.

• One of you has blue eyes, the other has green eyes : here too, it’s a 50/50 chance! Baby has an equal chance of having blue eyes or green eyes.

• You and your partner have blue eyes : in this case, there’s little doubt—you can be almost certain that your baby will also have blue eyes.

So what does this look like in terms of probability? Discover our summary table:

Are light-colored eyes more sensitive than dark-colored eyes?

There’s a common belief that light-colored eyes are more fragile than dark-colored eyes—but is it myth or reality? It’s a myth. Contrary to this false belief, light-colored eyes are not more sensitive to light than dark eyes . As explained in the previous paragraphs, it is the concentration of melanin in the superficial layer of the iris that influences its color and pigmentation. However, it is the second layer of the iris—brown in all individuals—that protects the retina from sunlight. Therefore, no eye color makes the eyes more sensitive. Good news, isn’t it? :)

What are heterochromatic eyes?

If there’s one trait that fascinates and intrigues, it’s heterochromia! We talk about heterochromia, or heterochromia, when an individual has two different eye colors. All combinations are possible: one blue eye and one green eye, or even one brown eye and one green. It can also appear as a brown spot in a blue or green iris. This peculiarity is related to an excess or a deficiency of melanin. Of course, this difference in pigmentation is extremely rare and most often hereditary; the probability that your little adventurer could have it is minimal.

The color of babies’ eyes fascinates us and melts our hearts! Blue, green, or brown—it’s hard to predict exactly which color will dominate your baby’s gaze. Although it doesn’t really matter, our parent hearts will inevitably melt in front of those eyes. Still, it’s possible to make a few predictions by looking at the eyes of the parents and grandparents. So, shall we place our bets? :)