It is considered that there are seven primary, central colors, and all the other colors are a combination or derivation of them.
These seven colors are: red, orange, yellow, green, blue, indigo, and violet. The rainbow colors, as we are taught as children.
Estimating all the possibilities, scientists say there would be DECILLIONS of different colors.
However, the human eye perceives up to a maximum of 10 million different tones. Which, to be honest, isn’t too bad.
With all this data, it’s normal that there is also an immense variety of colors in people’s hair and eyes.
The Four Hair Colors and Their Causes
It is accepted that hair has four basic natural colors:
- Black: High concentration of eumelanin.
- Brown: Depends on the tone, but the concentration of eumelanin is higher than that of pheomelanin.
- Blonde: Again, depends on the tone, but in this color, the concentration of eumelanin is lower than that of pheomelanin.
- Red: High concentration of pheomelanin.
There are scales that go into more detail for classification.
The Fischer-Saller scale, for example, establishes 8 primary human hair colors, which would be: black / dark brown, medium / light brown, dark blonde, medium blonde, light blonde, very light blonde (or platinum), reddish blonde, and red.
Most scales exclude one hair color, or rather, the absence of color: gray hair. The white color of hair without pigment.
These variations come from only two pigments: eumelanin and pheomelanin. Both are considered types of melanin.
- Eumelanin is formed by the oxidation of tyrosine into melanin, followed by a polymerization that leads to derivatives of dihydroxyindole, which we will call DHI and DHICA. We are not a chemistry blog, no need to get into details.
- Pheomelanin is similar, but instead of dihydroxyindole, it has compounds with the amino acid cysteine. This amino acid has a particularity that pheomelanin also possesses by incorporating it: the presence of sulfur in its formula.
The Genetic Reasons for Hair Color
Hair color is genetic. It is a polygenic characteristic. Different genes participate, contributing to the final result.
That’s why hair color and brightness are very hereditary. It is estimated that the heritability of hair color in children is between 61% and 99%.
But the colors do not have the same strength. Dark hair tones are dominant traits, compared to light tones, which are recessive.
That’s why a family with black hair can have a blonde child. The genes for blonde hair were in both parents, but the ones responsible for black tones were “covering” them.
With so many factors, the tellmeGen genetic analysis gives you a very accurate probability of your hair tone, but it’s impossible to be completely sure.
Blonde color is currently associated with 200 different genetic variants.
It is likely that the most studied gene related to hair color is the MCR1 gene. This gene encodes the information for the melanocortin 1 receptor, and it is found in areas such as the skin or eyes.
When the receptor is activated, the signaling pathway triggered leads to the production of eumelanin. If it is turned off or blocked, melanocytes produce pheomelanin instead.
The different forms of this gene have been linked to the likelihood of being red-haired, although to be red-haired, recessive alleles are needed. It is also involved in pathologies such as melanomas, including cutaneous malignant melanoma.
The time to start getting gray hair also seems to depend on genetics. This process is known as acromotrichia or canitie. The most studied gene on this subject is the IRF4 gene. There are variants associated with less melanin storage and therefore greater loss of color.
From a practical point of view, black hair is better for the sun. Eumelanin dissipates more than 99.9% of the UV radiation absorbed. Pheomelanin absorbs less and reflects more, which is why it appears with blonde and red tones.
One detail, both types of melanin are pigments, not proteins. Pigments are any substance whose function is to absorb and disperse specific wavelengths of light. Since this affects color perception, we can also say that their function is pigmentation.
The Six Eye Colors and Their Myths
Eye color is another polygenic trait. Eye color is defined by genetics, and therefore, it is also hereditary.
The clarity of the eyes depends on the amount of melanin they contain in the iris, including its density and distribution. In this sense, they are similar to hair.
It is accepted that there are six main colors: brown, hazel, blue, green, gray, and amber.
The more melanin, the darker the eye (brown), and the less melanin, the lighter the eye (blue). Green would be an intermediate color. With the exception of some, many of which are due to pathologies, all eye colors are found in a tone between brown and blue.
In genealogy and inheritance studies, it is common to use these traits for representations. Brown is a dominant trait, and blue is recessive.
Again, just like with hair, there are dominant and recessive colors. Two brown-eyed parents can have a green-eyed child and another with blue eyes.
Even two blue-eyed parents can have a brown-eyed child. No, it’s not that the child inherited the eyes of their grandparent. It could be due to atypical recessive variants for the brown color, hidden in the parents, or mutations that occur in the gametes (sex cells) and/or during pregnancy.
The color of the eyes does not skip generations following any ancestral custom. Genes are very serious in their work.
The reality is, as usual, much more complex. It is impossible to predict with absolute certainty the eye color a baby will have.
The DNA That Decides Your Eye Color
More than 150 genes have been discovered that influence eye color. However, the contribution of each one is far from the same. Imagine the incredible variety of pigmentation in the iris that arises from this.
Eye color is hereditary, but many genetic factors contribute to it.
The main genes involved in the inheritance of eye color are:
- EYCL1: Determines the green and blue color in individuals.
- EYCL2: The main gene responsible for brown color.
- EYCL3: Determines the amount of melanin produced by the body.
Within blue eye genetics, a gene has been widely studied: OCA2. This gene gives rise to a protein that participates in the synthesis of melanin, and it has been linked to different types of albinism, such as oculocutaneous albinism.
Another gene commonly researched is HERC2. Interestingly, among its functions is the ability to activate or deactivate the OCA2 gene, thus affecting eye color. Some experts believe its importance is even greater than that of OCA2 itself.
As you can see (pun intended), it’s a complex and vast topic. We’re short on space here.
The tellmeGen genetic analysis gives you an estimate of your eye color based on your genetic variants, and the influence they have on making your eyes lighter or darker.
For example, a person may have medium eye clarity due to their genetics. The number of variants and their importance for light and dark tones would be very similar in both cases. Most likely, they would then have light brown or green eyes.
