According to an article in Siemens' Innovations Report, one person is responsible:
New research shows that people with blue eyes have a single, common ancestor. A team at the University of Copenhagen have tracked down a genetic mutation which took place 6-10,000 years ago and is the cause of the eye colour of all blue-eyed humans alive on the planet today.
“Originally, we all had brown eyes”, said Professor Eiberg from the Department of Cellular and Molecular Biology. “But a genetic mutation affecting the OCA2 gene in our chromosomes resulted in the creation of a “switch”, which literally “turned off” the ability to produce brown eyes”.
More science at the link.