why some people has blue eyes?
The blue eye colour is the result of collective contribution from two factors
Phenomenon of blue eye colour is very much similar to the blue colour of the sky.
In case of blue eye colour, concentration of melanin ( pigment) is less in the iris stroma . This causes the absorbtion of longer wavelength of light and reflection of shorter wavelength light by the underlying iris epithelium.Thus, blue colour light is reflected resulting in blue colour of the eye.
Concentration of melanin is decided by the genes.
The eye colour inheritance is a complex phenomenon which involves more than one gene and around 15 genes are involved in the determination of eye colour.