There is potentially a connection between diet and eye-color. Certainly, humans are genetically predisposed
to one eye color or another, but many people experience subtle or overt changes in the colors of the iris.
This phenomenon occurs most frequently in children. About 43% of children go through at least one change in eye color, between the ages of 3 months and 6 years. Usually, this change is a shade or two lighter or darker, but sometimes the color changes drastically, from brown to blue, for example.
According to the Archives of Opthalmology, 10-15% of adolescents and adults undergo spontaneous changes in eye color at least once.
The theory is that eye color is directly affected by the production of melanocytes, various chemicals that form melanin, a pigment of the human body.
Diet can affect nearly every chemical reaction in a body, from protein synthesis to neurochemical activity. Science itself suggests that certain chemicals may have a direct effect on eye color; Xalatan, a medication to treat glaucoma, is known to cause the iris to darken. I myself have noticed a distinct change in my own eye color while on the prescription antidepressant Paxil; over the space of a month, my normally dark brown eyes lightened a number of shades, becoming a brown-flecked gold color.