Science fiction is often used to show us the world through impossibly alien eyes. But there are fully human people who see the world in an alien way (to the rest of us) via current biological means. One of the most everyday versions of this is basic colorblindness. But what do people really see, when they see the world differently?

If you're in possession of a matching pair of X chromosomes, it's unlikely you could know what it's like to be colorblind. Biological females have between a 0.1 and 0.4 percent chance of being red-green colorblind. The most predominant form of colorblindness is the loss of reds and greens, both of which depend on L-cones in the retina to be seen by the brain. The gene that is responsible for these is on the X chromosome. Unless you are the daughter of a colorblind father and a colorblind or colorblindness carrier of a mother, you'll always have a back-up. If you have an X and a Y chromosome, and your mother is a carrier, you've got a fifty-fifty shot at being colorblind in this way, which adds up to between five and seven percent of the population.

The most mild type of colorblindness is Deuteranopia, which takes out most shades of red and pink and turns them into a green. A red dress, provided that it's light, will turn into a sort of dull shade of army green. Greens are also darker and duller, turning to light grays and brownish-green camouflage colors. An often unappreciated casualty of red-green colorblindness is purple, which is red and blue mixed together. Deuteronopia turns purple to just another shade of blue.


Protanopia is more severe. Instead of turning red to green, it shuts some shades of red off completely, making them appear black or gray. The darker shades of red are gray-black, and even the lightest shades of pink change to army green or darker. Skin tones are often wiped out. A little more of the bright shades of green get through than do through Deuteranopia, though.

The most uncommon form of colorblindness is yellow-blue colorblindness. This one isn't sex-selective at all. It's the result of defective S-cones, which could be unformed due to genetics, but can also be damaged through other activities. Alcoholics have a higher rate of this colorblindness, called Tritanopia, than the rest of the population's 0.01 percent. Head injuries and exposure to some kinds of industrial chemicals can also take out blue-yellow color vision. It's understandable that Tritanopia is dubbed yellow-blue colorblindness, to distinguish it from red-green colorblindness, but it takes out green more completely than any other kind of colorblindness. All greens are gone, transmuted to blue. Reds are also changed, turned to pink. But yellow is also destroyed, and is also turned completely to shades of pink. Pink skin is more florid. Even the blue shades are changed, seeming grayer and darker.


Images: Color Blind Awareness

Via How Stuff Works, HHMI, and Colour-Blindness.

Note: Deuteranopia and Protonopia look very much alike. I would recommend hitting the How Stuff Works (in the links here) site for more images that demonstrate the difference.