About 6,000 to 10,000 years back during the Neolithic age the genetic mutations lead to blue eyes. As per the researchers it is said to have all started from Europe where humans started residing near the Black sea.
As per the researchers blue eyes exist from an common ancestor.
Earlier all humans just had brown eyes and later due to the genetic mutations which was adapted by genes and later transmitted from one generation to another.
This then became dominating over the brown eyes. This switch leaded to the blue and later green eyes.
The following chart explains the consequences of eye color