Is green the rarest eye color?

Yes, green is the rarest colour of human eyes, and it is most dramatic in North African people, probably because of its contrast with coffee coloured skin. Brown-eyed people are not that common, only 5.9% of the world population, but only around 2% has green colored eyes.

Green eye color occurs when there's a mild amount of pigmentation in the eye with a golden tint. It's thought it is caused by the migration of peoples from North to south.