Melanin is the pigment that changes people's skin,hair and eye color. The more melanin present the darker the eyes will appear. So, obviously, people with brown eyes have more melanin and lighter shades(blue/green) have less.

Besides giving our eyes color, melanin helps protect them from the sun. While all eyes have sensitivity to the sun’s harmful rays, light eyes are much more sensitive to the sun's ultraviolet (UV) rays than darker eyes because they have less pigment.

Both urobilin and phytochrome are also types of pigment. Phytochrome is found in plants and urobilin is the pigment that turns your urine yellow. Melatonin isn't a pigment at all, its a hormone produced by the pineal gland that regulates sleep and wakefulness.

On a side note, eye color has been the source of superstition through the years. The mystically-inclined believe the eyes are the windows to the soul and eye color shows a person's talents. Some personality traits attributed to eye color are: Blue-eyed people have rich imaginations.Those with green eyes have sharp minds.Hazel eyes indicate passionate souls.People with brown eyes are calm but have underlying passion.

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