Eye color changes shortly after birth, as all babies are born with blue eyes and then once their melanin starts to develop, their eye color may change to become darker and/or more varied.
Interestingly, some people also have eye color changes around puberty, much like the reported hair texture changes many women experience around this time.
According to a Genetics.TheTech.Org study, 15% of Caucasians reported a lightening or darkening of their eye color around the time of puberty. Eye color and its change are determined by multiple genes and how those genes influence the pigment in one’s eyes. Genes are protein recipes which explains how the proteins in your eye will make up and change its color.
Specifically, the eye protein melanin and its ratio of eumelanin to pheomelanin as well as its distribution, cause the eye color differences found in the human population today.
Eye disorders and eye surgery can cause permanent changes in eye color as well. Heterochromia, a condition where one person has eyes that are each a different color can be healthy and normal, however it can also be caused by trauma, shaking loose melanocytes in only one of the eyes, making that eye appear lighter or darker than it originally was. It can also be a signal of a disease such as Horner’s syndrome. Late stage diabetics may also see their eyes darken. Other than those conditions, seeing one’s eyes change drastically throughout one’s life is quite rare.
Eye color can change temporarily as well as permanently, and this is based on situational factors such as the amount of sunlight in a space and your body’s aroudal.
How excited, calm and aroused you are can affect the color of your eyes, mainly by how it affects your autonomic nervous system and corresponding pupil dilation. When excited, the eye becomes much darker as the pupil enlarges and causes its black surface to cover more surface are of your eye. This also happens in the dark, as your pupil will expand to let in as much light as possible. This is why professional poker players wear sunglasses even inside, to cover their pupil dilation so competitors cannot tell when they are excited with a very good hand.
When you are calm or in very bright places, your pupil will shrink and cause your eye color to become lighter as well as show more of your natural color as opposed to your black pupil.
Human eyes do not change color with emotion, a common myth expressed in YouTube videos and popular media. Pupil dilation, which is affected by arousal as explained above, does affect the ratio of the pupil to eye, but the physical color of the eye stays the same.
Another factor that influences temporary eye color is the color of your surroundings and clothing. Light is reflected off your surroundings and clothes and may affect how other people perceive your eye color as it picks up on the surrounding reflections.
Adult people that have European ancestors have the most varied eye color history that includes shades of blue, green, hazel, and more bright effervescent colorings, however all other people have differing shades of brown eyes.
A common myth is that the ‘blue’ eye is a recessive gene, which was found by a Davenport and Davenport (1907) study. This would mean that two parents with blue eyes would only have the possibility of having a blue eyed child. In follow up studies, it has been found that two blue eyed parents often have other eye colors such as brown or gray, indicating eye color genes are more complex and varied than the Davenport study originally indicated.
Although eye color is not as simple as was once thought in regards to dominant and recessive genes, two parents with blue eyes are still much more likely to have a blue eyed child than two parents with dark brown eyes. The interaction of genes is complex, but there are still patterns we are able to observe.
There are many genes that play a role in eye color determination, including the HERC2 and OCA2 genes which sit side by side on chromosome 15, however it has been found that more than 10 other genes interact in complex ways to play a role in final eye color determination. (Sturm and Larsson 2009) (Lie et al 2010) (Pospiech et al. 2011).
Eye color can range from dark to light with a variety of interstitial colors. See the following chart for possible variations in eye color:
The most popular eye color that people think is attractive, according to an All About Vision poll, is green, gathering 20.3% of the votes, light blue in second and then hazel coming in close at third.