Well, it is normal to have this kind of symptom. So you don not need to worry about it. As we know that exposure to light after birth triggers the production of melanin in the iris of the eye. By three years of age, the eyes produce and store enough melanin to indicate their natural shade. While changes in eye color of infants are more common, even in adults, eye color changes are seen, most often as a result of exposure to the sun. Sunlight triggers melanin production in the eye, as it does to the skin. People with green eyes in the winter might develop darker, more hazel eyes if they spend more time outdoors.