The identity of the colors was always fertile territory for teenage philosophers. "What if my green is different from your green?" thousands of miniature Platos have mused to each other over the years, gazing at lava lamps, asking for another dose of PHILOSOPHER FUEL.
Until we can stick cameras into our consciousness, we simply don't know whether the qualia of color differs from person to person. What we do know is that about eight percent of the male population is colorblind.
So what is color blindness anyway? Our eyes are made up of rods and cones. Rods give us black and white. Cones give us color. People with 'normal' color vision have three different kinds of cones. The color blind suffer by with only two.
Most mammals have only two kinds of cones. And most birds have an astonishing four kinds of cones--which means that they can see into the ultraviolet range and can write poetry about flowers and sunsets just that smidge more expressively.
It is one of those enduring mysteries--what does it actually mean to see a color that you hadn't before? What does it actually mean that I can see a color that my colorblind colleagues could not even imagine?
I'm reminded of Terry Pratchett's the Colour of Magic, a book I marinated my brain in when I was a little me. In it, the presence of magic can be detected by the presence of color otherwise non-existant. Except, I guess, by birds.
Inspired by the legendary Cecil Adams' Straight Dope.