Eyes come in a variety of colours, ranging from common shades like brown and blue to rarer hues like green, grey, and hazel. While brown eyes are the most common worldwide, accounting for over half of the global population, certain eye colours are much less frequently seen. The rarest eye colours among humans owe their striking appearances to unique genetic mutations and low prevalence among ethnic groups. Understanding the origins and genetics behind eye colour rarity provides fascinating insights into human ancestry and evolution.
In this article, we will countdown the top 10 most rare and unusual eye colours in the world. Factors considered include global frequency, geographic distribution, and genetic uniqueness. For each eye colour, we explore its distinctive genetic mechanisms, geographic spread, and how it manifests visually.
The Genetics Behind Eye Colour
Human eye colour originates from the amount and type of melanin pigment found in the iris. Melanin comes in two forms: eumelanin which produces brown and black hues, and pheomelanin which produces yellow and red hues. The combination and concentration of these melanins determines eye colour.
Here are the key genes involved:
HERC2 – regulates OCA2 expression and melanin production
OCA2 – produces melanin
SLC24A4 – modifies amount of melanin
TYR – encodes tyrosinase enzyme for melanin production
Mutations in these genes can reduce melanin content and create uniquely coloured eyes. We’ll see how this plays out for each rare eye shade.
10. Red
True red eyes are extremely rare globally, but are most prevalent among certain groups:
Albinism – Lack of melanin causes translucent irises that reflect red retinal blood vessels. 1 in 17,000 people have oculocutaneous albinism worldwide.
Genetic mutations – Specific mutations in HERC2, OCA2, SLC24A4 cause low melanin and reveal red.
| Frequency | Less than 1% worldwide |
| Genetics | Albinism, HERC2, OCA2, SLC24A4 mutations |
| Distribution | Albinism – pan-global, Genetic – Northern/Eastern European |
True red irises are visually striking yet extremely rare. They originate from either melanin deficiency or unique genetic variants inhibiting melanin synthesis. Predominantly found among albinism patients and select ethnic groups, red eye colour stands at the top of the rarity scale.
9. Violet
Violet eye colour results from a dark blue and red pigmentation blend:
Melanin amount – Lower levels of eumelanin give blue hue.
Tyrosine deposits – Higher levels of pheomelanin give red/violet hue.
This unusual combination is primarily seen in Northern and Eastern European countries:
| Frequency | 2% worldwide |
| Genetics | Low eumelanin, high pheomelanin |
| Distribution | Northern and Eastern European |
The vibrant violet eye shade remains quite rare even among European populations. Its jewel-toned hues straddle the line between blue and red eye pigments. Subtle variations in melanin content gradate violet eyes from deep purple to pale lavender.
8. Green
Green eye colour arises when eumelanin levels are extremely low yet some melanin remains present:
Melanin amount – Low quantities of eumelanin give green-hue.
Rayleigh scattering – Blue wavelengths reflect off low melanin and combine with pheomelanin.
| Frequency | 2% worldwide |
| Genetics | Low eumelanin, medium pheomelanin |
| Distribution | Central, Western Europe and West Asia |
The rare green eye shade requires a precise melanin ratio. While found across continents, it occurs more frequently among European and West Asian peoples. Bright jade hues distinguish truly green eyes from hazel varieties.
7. Amber
Amber eyes derive from a golden yellow melanin hue:
Melanin amount – Moderate eumelanin levels produce amber tone.
Lipochrome pigment – Lipids and carotenoid deposits add yellows.
Amber eyes are extremely rare globally but concentrated in certain regions:
| Frequency | Less than 1% worldwide |
| Genetics | Moderate eumelanin, lipids, and carotenoids |
| Distribution | Southern Europe, West Asia, North Africa |
The amber eye colour results from a delicate combination of yellow pigments. Limited populations in Mediterranean regions and Western Asia exhibit this rare hue. When light catches amber eyes, they emit a warm golden glow.
6. Gold
Similar to amber, gold eye colour also contains a rich yellow melanin presence:
Melanin amount – Low to moderate eumelanin provides gold tone.
Lipochrome pigment – Lipids and carotenoids enrich colour.
However, gold eyes have key distinctions:
| Frequency | Less than 1% worldwide |
| Genetics | Low eumelanin, high pheomelanin and lipochromes |
| Distribution | Northern and Western Europe, West Asia |
The metallic, shimmering quality of gold eyes comes from low melanin allowing light reflection. While still extremely rare, gold eyes occur slightly more often than amber among European and Western Asian groups. The brilliant gold eye colour remains quite elusive worldwide.
5. Grey
Grey eyes have low to no melanin present, allowing the fibrous iris structure to reflect light:
Melanin amount – Very low levels of both eumelanin and pheomelanin.
Rayleigh scattering – Collagen fibres reflect and scatter light.
| Frequency | Less than 2% worldwide |
| Genetics | Extremely low melanin |
| Distribution | Northern and Eastern Europe |
With essentially a complete melanin absence, the translucent grey eye colour is quite rare. It also has limited ethnic association, as melanin deficiency can occur randomly across populations. The icy, misty hues of true grey eyes enthrall with their rarity.
4. Black
In contrast to grey eyes, black eyes have extremely high concentrations of melanin:
Melanin amount – Very high levels of eumelanin.
Thickness – Dense iris stroma obscures other pigments.
| Frequency | 2% worldwide |
| Genetics | Extremely high eumelanin |
| Distribution | Southern Asia, Middle East, Mediterranean |
The deepest onyx hues distinguish truly black eyes. Ethnicity plays a stronger role, as populations originating in Asia and the Middle East tend to exhibit highest eumelanin levels. The coal-dark colour arises from heavy melanin saturation rather than pigment absence.
3. Blue
While relatively common in Caucasian populations, globally blue eyes are rare:
Melanin amount – Extremely low quantities of melanin, especially eumelanin.
Rayleigh scattering – Short blue light waves scatter and reflect off collagen.
| Frequency | 8% worldwide |
| Genetics | Low melanin, HERC2 mutation |
| Distribution | Northern and Eastern Europe |
The vivid cerulean hues of blue eyes stem from low melanin levels combined with collagen scattering. Ethnicity also plays a role, with prevalence among Europeans due to genetic mutations like HERC2 that inhibits melanin production. While the blue eye colour is regionally common, it remains globally rare.
2. Heterochromia
Heterochromia iridium is a condition where the eyes have multiple colours. Patterns include central heterochromia with distinct inner and outer iris rings, along with complete heterochromia where each iris differs in colour.
Melanin levels – Varying melanin distribution in each iris.
Genetic factors – Chromosomal mosaicism, inherited conditions like Waardenburg syndrome.
| Frequency | 0.6% worldwide have complete heterochromia |
| Genetics | Chromosomal mosaicism, inherited syndromes |
| Distribution | Global |
Heterochromia stands apart from single colour varieties. Its multicolored mosaic irises are visually unique. The intriguing condition can occur randomly or result from inheritable syndromes. Even partial heterochromia is considered rare.
1. Ocular Albinism
The rarest eye colour is seen in ocular albinism, with prevalence of just 1 in 50,000 people worldwide. Ocular albinism only affects the eyes, preserving normal pigment in the hair and skin unlike full body albinism. Key distinctions include:
Melanin amount – None, resulting in red colour from blood vessels.
Nystagmus and photophobia – Involuntary eye movements and light sensitivity.
| Frequency | 1 in 50,000 worldwide |
| Genetics | GPR143 gene mutation |
| Distribution | Global |
The complete melanin absence in ocular albinism produces the rarest and most visually dramatic eye colour. Additional vision defects accompany the symptom. This X-linked disorder represents the pinnacle of eye colour rarity.
Conclusion
This countdown of the top 10 rarest eye colours worldwide reveals the genetic secrets behind unusual shades of red, violet, green, amber, gold, grey, black, blue, heterochromia, and ocular albinism. While eye colour prevalence differs regionally and ethnically, certain hues stand out as globally uncommon. The interplay of melanin types and amounts combines with Rayleigh scattering and genetic mutations to generate these visually striking irises. Rarity itself captivates human curiosity and attention. Though brown eyes dominates globally, we remain fascinated by exotic eye colours at the far end of the occurrence spectrum.
