As a geneticist with a focus on human genetics and traits, I can tell you that the combination of red hair and blue eyes is indeed considered rare, particularly because each trait is independently uncommon.

Red hair is caused by a variant in the MC1R gene, which is responsible for producing melanin, the pigment that gives color to our hair, skin, and eyes. This variant is most commonly found in people of Northern or Western European descent, such as those from Scotland, Ireland, and Wales. The frequency of red hair can range from as low as 1% in many populations to around 10-13% in some areas of Northern Europe.

Blue eyes are the result of a different genetic variation, specifically a switch in the HERC2/OCA2 gene complex that reduces the production of melanin in the iris. The allele for blue eyes is most prevalent in populations of Northern European ancestry as well. The global frequency of blue eyes is estimated to be around 8-10%.

When considering the combination of both traits, the rarity is compounded because you're looking at the intersection of two independently rare genetic traits. While there are no exact global statistics for the frequency of people with both red hair and blue eyes, it is generally agreed upon that this combination is much less common than either trait on its own.

read more >>

Red hair is associated with the gene MC1R, a recessive and somewhat rare gene that occurs in only about 2 percent of the world's population, according to the National Institutes of Health. ... Rarest of all are redheads with blue eyes. The majority have brown eyes or hazel or green shades.read more >>