tetrachromat

Light comes in three basic flavors: red, green, and blue - or so I thought. The standard operating procedure for vision is that Humans (along with primates, and a few other critters) have visual color perception that allows us to distinguish approximately 100 different shades of each of the three colors of light. Mixing and blending these colors in combination allows us to see millions of distinct hues - we are natural trichromants.

However, there are some women who can see four basic wavelengths of light. From Damn Interesting: "In an odd twist of fate, the same genetic glitch that creates color-blind males may create females with better-than-usual color vision." A small percentage of women are capable of detecting a range of color that exists between in a "orange-ish" spectrum. It may be impossible for trichromats to imagine what the world looks like to a tetrachromant.

Genecists have been aware of this acute visual perception for years. According to the Wikipedia, "some birds, fish, amphibians, reptiles, arachnids and insects" are known tetras, and a butterflies might be able to see 5 full wavelengths of color, although their 4th wavelength is in the ultraviolet range, beyond the human eye's capabilities.

Detecting the necessary genes for an enhanced color perception is one thing, to actually demonstrate that tetrachromants can see a range of colors that is an order of magnitude greater than the majority is another issue. Mothers of color blind sons have been tested on their visual perception and speed in color-differentiation. Researchers believe that while many women might have the genetic coding to be tetrachromatic, only a few can detect the "colossal range ... 100s of millions of colors" (approx. 2-3% of women).