I remember reading a few years ago that some cultures/languages don't differentiate between blue and green. I felt a little "snap" in my mind. It had always intrigued me that Wolof, the language I spoke when I lived in Senegal, had words for all the colors except blue - for which it adapted the French term. The author (I wish I could recall this source) speculated that if the language failed to differentiate between two shades, its speakers might not cognitively separate the two… might not even experience them as different colors. Now this article [No one could see blue until modern times] offers evidence that many earlier cultures had a paucity of words for color, and as a result, people simply didn't perceive colors the way most people do now.
That's just the beginning: the NPR/WNYC program Radiolab offers a mind-expanding hour exploring the nature of color. Radiolab is producing some of the finest programing for inquisitive people in any medium. If you're not already listening to their podcast, please correct that oversight. Sight… get it?