Well, as a matter of fact, the geographic distribution of different eyed people has got a lot of things to do with races and geographic conditions. Anyway, you could find a lot of green eyed people in Europe and America, as well as Australia, but blue eyed people seem to be more commonly seen in the world. Because their races and genetic issues. Anyway, green eyed people are less in numbers.
Eye colors are genetically different,it began with the ancient ,well,it may from different creatures.
Green eyes is rarer than most of the colors,like blue eyes and black eyes.
The reason differ from the ancient people inherit.
However,the environment people growing in can be include in the reasons.