Most people had brown eyes until about 10,000 years ago when a single genetic mutation from the Black Sea switched the eyes from brown to blue. Approximately 8% of the world’s population now has blue eyes.
https://www.google.com/search?source=hp&ei=U9rdXIjpFYbF0PEPlKq2iAo&q=Eye+color%3A+How+it+develops+and+why+it+changes&oq=Eye+color%3A+How+it+develops+and+why+it+changes&gs_l=psy-ab.12...1267892.1267892..1281705...0.0..0.164.164.0j1......0....2j1..gws-wiz.....0.ohog3FBfF4k
Thanks for adding the link Carl!