This is where blue eyes are the most common
Blue eyes can appear to be more or less common depending where in the world you are, as the phenotype is much more common in some places. In fact, sometimes the majority of people in an area have blue eyes. For example, 
if you were strolling through Estonia or taking a vacation in Finland, not having blue eyes would be rare, as 89 percent of the populations of those countries have azure irises, according to World Atlas. That’s a lot!
After that, there’s a significant drop, although blue eyes are still the majority in Ireland and Scotland, at 57 percent and 50 percent, respectively. England is next on the list with 48 percent, while 45 percent of people in Wales have baby blues. Belgium and France clock in at seventh and eighth on the list, with 28.9 percent of people in the former having blue eyes and 20.2 percent having blue eyes in the latter. Finally, at places nine and ten are the United States and Spain, both with just over 16 percent of the population possessing cerulean eyes.
Everyone with blue eyes has a common ancestor
Plenty of people have blue eyes today, and there have been people with blue eyes for thousands of years. But believe it or not, that wasn’t always the case. Thanks to the scientists at Copenhagen University, we now know that somewhere between 6,000 and 10,000 years ago, everyone had brown eyes, according to Science Daily. But at some point during that time, a mutation occurred on the OCA2 gene, which controls how much melanin we produce. Specifically, this mutation essentially acted like a «switch» and «turned off» people’s ability to produce brown eyes. Thus blue eyes were born!
Not only did the team at the university identify the mutation that created blue eyes, but they also discovered that everyone with blue eyes has something in common. «From this we can conclude that all blue-eyed individuals are linked to the same ancestor,» said Professor Hans Eiberg. «They have all inherited the same switch at exactly the same spot in their DNA.» That’s unlike brown-eyed folks, who have significant differences in their DNA related to melanin production.
This is why it looks like blue eyes change color
If you are the lucky owner of a set of cobalt peepers, chances are you’ve noticed that your eyes appear to change color, sometimes looking bluer or grayer — or even lighter or darker. That was certainly the case with the famous movie actress Elizabeth Taylor, whose bright blue eyes could look violet when the light hit them just right.
There’s a reason blue eyes appear to change color, which is related to why they look blue in the first place. You guessed it: It all depends on how much light is both coming into and reflecting out of the eye, according to the American Academy of Ophthalmology. Additionally, the color of the eye can look different depending on the color of clothing that a person wears, as well as the color and style of makeup that’s applied around the eye.
To be fair, people with green and hazel eyes are also prone to seemingly color-changing irises as well, so this isn’t unique to blue-eyed folks. But it’s notable nonetheless.
Why do some babies’ blue eyes turn brown?
If you’re a parent, or are close to someone who’s had a baby, you might have had the experience of watching the eyes of an infant change color from bright blue to green or brown. That’s why you can’t know what someone’s eye color will be when they grow up until about the six-month mark, according to an article published by McGill University.