The authors concluded that the mutation may have arisen in a single individual around the Black Sea region 6,000-10,000 years ago, perhaps suggesting that all people with true blue eyes are more closely related. However, blue eyes with brown spots around the pupil are not related to this mutation.^[22]

Blue eyes are most common in Poland^[23], Ireland^{[24] [25]} , Netherlands^[26], Iceland^[27] , Austria^[28], Sweden^[29], Norway^[30], Denmark^[31], Russia^[23], Finland^[32], Germany^[33], France^[34], Estonia^[35], and the United Kingdom^[36][37] They are also present in Southern Europe, Spain^[38], Portugal^[39],Italy^[40] and the Balkans ^[41], the Middle East ^[42] (especially in Israel and Lebanon), India and are also found in Afghanistan. A 2002 study found the prevalence of blue eye color among Whites in the United States to be 33.8% for those born from 1936 through 1951 compared with 57.4% for those born from 1899 through 1905.^[7]

Brown

Brown human iris

Light brown human iris

Brown eyes are predominant in humans^[43] and, in many populations, it is (with few exceptions) the only iris color present.^[44] It is less common in countries around the Baltic Sea, such as Finland and Estonia. Germany has also shown signs that many people have dark brown eyes.

In humans, brown eyes contain large amounts of melanin (eumelanin) within the iris stroma, which serves to absorb light, particularly at the shorter wavelengths.^[5][21] Very dark brown irises may appear at a glance to be black.^[45][46]
 

 Gray

A steel blue-gray eye

Gray eyes have less melanin than blue eyes, even though they are considered a darker shade of blue (like blue-green). They are most common in European Russia, Finland and the Baltic States. Under magnification, gray eyes exhibit small amounts of yellow and brown color in the iris.

A gray iris may indicate the presence of a uveitis. However, other visual signs make a uveitis obvious.

Visually, gray eyes often tend to appear to change between the shades of blue, green and gray. This is said to be influenced by the lighting and the surroundings (such as clothes, makeup, etc.).

The Greek goddess Athena was renowned for having "owl-gray" (in Greek, γλαυκῶπις – glauk¨­pis) or "sea-gray" eyes.^[47]
 

Green

Green eyes

The most unusual color, only 1-2% of the the world population have true green eyes. Green eyes are the product of moderate amounts of melanin. According to some researchers, green eyes are the result of mutations that change the melanin structure ^[48] Green eyes are most common in Europe ,Norway and to a lesser extent in the Middle East, Northern parts of India, Pakistan, and Afghanistan and Mexico. 88% of the Icelandic population have either green or blue eye color