Eyes that appear bluish green in color are often referred to as “greenish blue” or “blueish green”. There is some debate around the exact terminology, but most eye care professionals and researchers agree that these eye colors fall somewhere in between pure blue and pure green on the eye color spectrum.
The Eye Color Spectrum
Eye color is determined by the amount and quality of melanin pigment in the iris. Brown eyes contain a lot of melanin, while blue eyes contain very little. Green eyes fall in the middle with an intermediate amount of melanin.
However, eye color is more complex than a simple spectrum from brown to green to blue. There are many subtle variations and combinations that create the full range of human eye colors.
For example, hazel eyes appear greenish brown or yellowish brown. Gray eyes have a dark gray ring around the iris with a lighter gray inner color. Even blue eyes can have flecks of gold, brown, or green in them.
The eye color spectrum can be visualized as:
Brown -> Hazel -> Amber -> Green -> Blueish Green -> Greenish Blue -> Blue -> Gray
As you move from brown to blue, there is less melanin overall. But there can be complex mixing and layering of pigment that creates hybrid eye colors between pure green and pure blue.
What Causes Bluish Green Eyes?
Bluish green, or greenish blue, eyes occur when there is a low to intermediate amount of melanin in the iris, but it is distributed in a unique way that creates a hybrid of blue and green coloring.
Here are some of the factors that can contribute to eyes appearing more blueish green or greenish blue:
- Having less melanin overall than brown or black eyes, but more than purely blue eyes
- A scattering effect of light on minimal pigment that brings out hints of blue
- A ring pattern in the iris that is predominantly green on the outer edge and blue nearer the pupil
- A blue melanin pigment called lipochrome that combines with low levels of the brown pigment eumelanin
- Deposits of collagen in the stroma that reflect light to produce bluish hues
The unique blend of different pigments and structures in the iris allows more blue hues to show through the green, creating a mixed color.
Genetics of Bluish Green Eyes
As with most eye colors, genetics play a major role in determining whether someone will have greenish blue or blueish green eyes. Some key genetic factors include:
- The HERC2 and OCA2 genes, which help regulate melanin production and distribution
- A genetic mutation near the OCA2 gene that reduces melanin and allows blue color to show through
- Inheriting intermediate amounts of melanin from parents with a mix of eye colors
- Genetic conditions like Waardenburg syndrome that affect melanin pigment formation
A bluish green or greenish blue eye color often occurs when someone inherits a version of the HERC2 or OCA2 genes associated with reduced pigmentation from one parent and a version associated with intermediate pigmentation from the other parent.
The interaction between these and other eye color genes leads to an iris with some melanin, but not enough to be purely green or brown. This allows for mixtures of blue and green.
Prevalence of Bluish Green Eyes
It is difficult to determine exact statistics given the ambiguity and subjectivity around eye color classification. However, some surveys and studies allow us to estimate the prevalence of greenish blue and blueish green eyes:
- Approximately 2-3% of the global population has either blueish green or greenish blue eyes
- In Northern and Western European countries like Iceland, the Netherlands, and Finland, up to 10% of people may have an intermediate blue-green eye color
- A study of Icelandic and Dutch adults found that nearly 8% had some variant of light blue-green eyes
- Among Caucasians, as many as 15% may have an in-between eye color with both blue and green aspects
Overall, bluish green or greenish blue eyes are much rarer globally than pure blue eyes or pure green eyes. But in certain geographic regions and ethnicities, intermediate eye colors can be relatively common.
| Country | Estimated Prevalence of Bluish Green Eyes |
|---|---|
| Iceland | 8-10% |
| Ireland | 3-4% |
| Netherlands | 8-10% |
| United States | 2-3% |
Types of Bluish Green Eyes
There are a few key patterns and variations that can create the appearance of bluish green or greenish blue eye color:
Central Heterochromia
This refers to eyes that have different colors toward the middle compared to the outer edge of the iris. For example, central heterochromia can result in a green outer ring with more blue hues around the pupil.
Iris Crypts
These are small, irregularly shaped areas in the iris that lack pigmentation. Light reflects off the collagen in the crypts, producing bright spots or streaks of blue in an otherwise greenish iris.
Sectoral Heterochromia
This is where a section or wedge of the iris contains a different color than the rest. A common version is a brown or gold section in an otherwise blueish green or greenish blue iris.
Low Melanin Concentration
A more uniform greenish blue or blueish green hue can occur when the iris simply has very low amounts of melanin overall. Light scatters off minimal pigment to reveal a mixed blue-green color.
Comparison to Other Eye Colors
It can sometimes be challenging to distinguish between different shades of green, blue, gray, and hazel eyes. Here are a few key ways bluish green eyes tend to differ from similar colors:
- Pure Green Eyes – Bluish greens have more blue hues mixed throughout and lack the vivid emerald green coloring of fully green eyes.
- Turquoise Eyes – Turquoise eyes appear more blue-green in equal measure, while bluish greens tend to have slightly more blue versus green.
- Blue Eyes – While bluish green eyes have some blue, the green tint muting the blue is absent in pure blue eyes.
- Hazel Eyes – Hazel eyes are more brown and orange than green, and lack the subtle blue hues of greenish blues.
- Gray Eyes – Gray eyes usually have a dark limbal ring on the outer edge and lack the green pigmentation of blueish green eyes.
Conclusion
Bluish green and greenish blue eyes have a mysterious, complex appearance that is quite rare globally. The subtleties in color come from specialized melanin and collagen patterns in the iris. These hybrid eye colors indicate a genetic background mixing the influence of blue and green eye DNA. While no eye color is intrinsically better, many find the alternating blue and green flecks or rings to be aesthetically stunning.
