Final answer:
People refer to the color of the iris when they talk about eye color. The iris is the colored part of the eye, lying in the middle layer of the eye, which adjusts the pupil based on light intensity.
Step-by-step explanation:
When discussing the color of one's eyes, people are referring to the color of the iris. The iris is the part of the eye that contains pigmentation and hence, gives the eyes their color. It lies in the middle layer of the eyeball, known as the vascular tunic, which also includes the choroid and the ciliary body. The iris works like a diaphragm, adjusting the size of the pupil in response to the intensity of light to control the amount of light that enters the eye.
The sclera is the white part of the eye, forming five-sixths of the eyeball's surface, more of which is visible in humans compared to many other species. The cornea, part of the fibrous tunic, functions as a transparent protective layer at the front of the eye, through which light enters. The lens, which is positioned behind the iris, works in conjunction with the cornea to focus light onto the retina.