人的眼睛的顏色 是有虹膜決定的,虹膜的顏色是由其組成的色素決定的，決定的根本是基因差異。
+ 基因一點點變異或畸變或突變 即可引起虹膜色素的變化。
這是指 同一人種的眼睛顏色不同，比如，藍色，綠色，灰色，黃色，棕色，深棕色（黑色）等；
不是指 不同人種的眼色差異。當然不同人種的眼睛顏色也是不同的。
The color of our eyes comes from the appearance of the pigment that is present in the iris, the central part of the eye. Brown eyes are rich in melanin pigment deposits, making them darker, while blue eyes lackmelanin. Heterochromia happens when the concentration and distribution of melanin isn't uniform.
波斯貓
甚至一隻眼睛的虹膜可有不同的顏色。
Heterochromia iridium (two different-colored eyes within a single individual) and
heterochromia iridis (a variety of color within a single iris) are relatively rare in humans and result from increased or decreased pigmentation of the iris. Most cases are isolated and sporadic, conceivably resulting from an alteration in the expression of the above-mentioned genes (and those we have yet to find) within the cells of the entire iris or even a particular section. Other potential causes include trauma around the time of birth or later in life, congenital pigmented nevi or even medications such as those used in the treatment of glaucoma. There are a few well-known syndromes of which heterochromia iridis is a striking feature. Waardenburg syndrome type 1, an autosomal dominant disorder caused by mutations in the PAX3 gene, is characterized by pigmentary disturbances of the iris, hair and skin, as well as congenital sensorineural hearing loss. But two different eye colors tends to be an isolated finding, which adds to the seemingly endless and fascinating variation in humans' physical characteristics.
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