The color of a person`s eyes is determined by the pigment present in the iris, which is the colored part of the eye. The iris contains pigments that determine the color, such as melanin. Melanin is a dark brown pigment that gives eyes their brown color. If the iris contains less melanin, the eyes will appear blue. A higher concentration of melanin will result in darker eyes, such as black.

Option 1: The pupil is the hole in the center of the iris that allows light to enter the eye, but it does not directly affect eye color.

Option 2: The cornea is the clear front surface of the eye that protects the iris and pupil. It does not contain pigments that determine eye color.

Option 3: The iris, as explained above, contains the pigment that determines eye color.

Option 4: The choroid is the layer of tissue located between the retina and the sclera (white part of the eye). It does not directly affect eye color.

In conclusion, option 3, the iris, is the correct answer as it contains the particular pigment that determines the color of a person`s eyes.