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Primary colors: primary only for us
![[John Meyer, N. Carolina State U] A flower, as we see it.](bloom1.jpg) Q: Why are red, green, and blue the primary colors? -Shirley E., Champagne, Illinois
A: What we call "primary colors" has nothing to do with the nature of light. It depends rather on how we
humans detect light.
[John Meyer, N. Carolina State U] A flower, as we see it.
"Color really refers to a sensation that a particular wavelength of light [produces]," says Brian DeBroff,
ophthalmology professor at the Yale School of Medicine.
![[John Meyer, N. Carolina State U] The same flower, as bees see it (recorded with ultraviolet sensitive film).](bloom2.jpg) Human eyes have two types of cells for absorbing light: rods and cones. You see little color at night. Consequently, the rods, used mostly for night vision, detect primarily light and dark. The cones detect
color and favor some colors over others. They absorb blue, green, and red light best. That's why those
colors are called "primary".
The same flower, as bees see it (recorded with ultraviolet sensitive film).
We perceive white when the cones absorb light containing equal amounts of the three primary colors. By
adding together primary-color responses, our eyes see almost any color.
How do we perceive light at all? Special pigments in the rods and cones absorb light energy and change it into chemical energy, which, in
turn, stimulates an impulse within a nerve cell, says John Meyer, entomologist at North Carolina State University.
Colors, however, aren't universal even among humans. Some languages don't have separate words for two primary colors: green and
blue, for example, even though these people see both colors. All languages name black and white. Eskimos use 17 words for white as
applied to different snows. If a language has a word for another color, it most likely is red, the color of blood.
Different species have different primary colors. Birds are sensitive to red. Bees are blind to red but can see ultraviolet-beyond our range
of color perception. Dogs can barely perceive any color.
(Answered by April Holladay, science correspondent, Apr. 24, 2002)
Further Surfing:
John Meyer, N. Carolina State U: Nectar guides
John Meyer, N. Carolina State U: color vision
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