It may be far in the future, but there's some kind of logical way to get from where we are to where the science fiction is.
Elizabeth MoonMost eyes have more than one color, but usually they're related. Blue eyes may have two shades of blue, or blue and gray, or blue and green, or even a fleck or two of brown. Most people don't notice that. When I first went to get my state ID card, the form asked for eye color. I tried to write in all the colors in my own eyes, but the space wasnt big enough. They told me to put 'brown'. I put 'brown', but that is not the only color in my eyes. It is just the color that people see because they do not really look atr other people's eyes.
Elizabeth Moon