# Could early man only see three colors? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [December 11, 2005, 1:20pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129 "2005-12-11T13:20:34Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![simian](https://avatars.discourse-cdn.com/v4/letter/s/d2c977/32.png) [@simian](https://boards.straightdope.com/u/simian)\ **Post date:** [December 11, 2005, 1:20pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/1 "2005-12-11T13:20:34Z")
I know it’s quite an old posting of cecils, but (there’s always is isn’t there) has anyone pointed out that there’s actually three visible colours (Red, Blue, Green) and all other colours are derived from these? And correct White is not a colour, nor is Black. See [http://www.straightdope.com/classics/a2\_168b.html](http://www.straightdope.com/classics/a2_168b.html) ---
**Author:** ![picunurse](https://avatars.discourse-cdn.com/v4/letter/p/7bcc69/32.png) [@picunurse](https://boards.straightdope.com/u/picunurse)\ **Post date:** [December 12, 2005, 10:34am UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/2 "2005-12-12T10:34:42Z")
> [@simian](#): > > I know it’s quite an old posting of cecils, but (there’s always is isn’t there) has anyone pointed out that there’s actually three visible colours (Red, Blue, Green) and all other colours are derived from these? And correct White is not a colour, nor is Black. > See [http://www.straightdope.com/classics/a2\_168b.html](http://www.straightdope.com/classics/a2_168b.html) Sorry, but you aren’t even close. Read a little about the [physics of color.](http://en.wikipedia.org/wiki/Color) White is the reflection of all color wave lengths. Black absorbs the whole spectrum. BTW, the three _Primary_ colors, which I believe, is what you’re referring to, are Red, Blue and _Yellow_, not Green. Green is a secondary color, combining yellow and blue. All colors in our visual spectrum are indeed, derived from the three primaries.The secondary colors are green (blue/yellow) purple (blue/red) and orange (red/yellow) The [color wheel](http://images.google.com/imgres?imgurl=http://www.sanford-artedventures.com/study/images/tertiary_triange_wheel.gif&imgrefurl=http://www.sanford-artedventures.com/study/g_color_wheel.html&h=280&w=279&sz=10&tbnid=hfZxfkURXNcJ:&tbnh=109&tbnw=108&hl=en&start=3&prev=/images%3Fq%3DColor%2Bwheel%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN) may answer any other questions you might have. ---
**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\ **Post date:** [December 12, 2005, 11:05am UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/3 "2005-12-12T11:05:05Z")
Nitpick: You’re _both_ right. There are two sets of primary colors. Since it’s 5 am and I haven’t had my caffeine yet I can’t remember the technical terms, but there is the set yellow-blue-red which are primary for pigments, and the red-green-blue set that is primary for light. A yellow pigment and a blue pigment give you a green pigment. A red light and a green light give you a yellow light. ---
**Author:** ![Arjuna34](https://avatars.discourse-cdn.com/v4/letter/a/eb8c5e/32.png) [@Arjuna34](https://boards.straightdope.com/u/Arjuna34)\ **Post date:** [December 13, 2005, 1:19pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/4 "2005-12-13T13:19:22Z")
Cecil has weighed in on this topic, too: [If blue, red, and yellow are primary colors, why do color TVs use blue, red, and green?](http://www.straightdope.com/classics/a3_344.html) Arjuna34 ---
**Author:** ![j2browning](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@j2browning](https://boards.straightdope.com/u/j2browning)\ **Post date:** [December 13, 2005, 7:55pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/5 "2005-12-13T19:55:31Z")
The strange thing about that column is the odd idea that the Greeks couldn’t see colors at all. Wonder what those “scholars” thought made the frescoes and mosaics appear so lifelike? ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 13, 2005, 8:27pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/6 "2005-12-13T20:27:02Z")
> [@](#): > > Read a little about the physics of color. Primary and secondary colors have nothing to do with physics, but rather with physiology. To creatures with different eyes than our own, red, green, and blue (or red, yellow, blue, or whatever) would not necessarily be the primary colors, and they might not even have the same number of primary colors we have. The might even see in a continuum of color, in which case _every_ color would be “primary”. Red light and green light do not together make yellow light, they make a light which is indistinguishable, _to our eyes_, from yellow light. If I had a red laser, a green laser, and a yellow laser, and I mixed the red and green together, a human would not be able to distinguish that from the yellow laser, but some other organism might, and a spectrometer certainly could (indeed, to the spectrometer, they would look _completely_ different, with no similarity at all). ---
**Author:** ![AnnaV](https://avatars.discourse-cdn.com/v4/letter/a/439d5e/32.png) [@AnnaV](https://boards.straightdope.com/u/AnnaV)\ **Post date:** [December 14, 2005, 12:17am UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/7 "2005-12-14T00:17:06Z")
I think some people are getting slightly confused between paint and light here. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [December 16, 2005, 4:45pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/8 "2005-12-16T16:45:53Z")
> [@j2browning](#): > > The strange thing about that column is the odd idea that the Greeks couldn’t see colors at all. Wonder what those “scholars” thought made the frescoes and mosaics appear so lifelike? Lifelike in _color_? Offhand, I don’t recall there being any surviving polychrome Greek art whatsoever. There _are_ historic color mysteries. Why does Homer repeatedly refer to “the wine-dark Sea”? Why do ancient astronomers call Sirius “red”? ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [December 16, 2005, 5:25pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/9 "2005-12-16T17:25:21Z")
> [@Chronos](#): > > The[y] might even see in a continuum of color, in which case every color would be “primary”. Is this really possible? It doesn’t violate any physical principles, but the engineering may not be feasible. Off the top of my head, I can’t think of any detection mechanism that would work. I believe every detector will preferentially detect some wavelengths better than others. So to detect light in a continuous manner, you’d need something analogous to the inner ear: an array of detectors, each tuned to a slightly different wavelength. This works well in the ear, because the each detector can sense or not the sound without attenuating signal. Is it possible to build something like this for light? ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [December 16, 2005, 5:43pm UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/10 "2005-12-16T17:43:43Z")
I’m inclined to think an _imaging_ true-spectrum system might not be possible, but a true-spectrum and source-direction system might be. ---
**Author:** ![scr4](https://avatars.discourse-cdn.com/v4/letter/s/59ef9b/32.png) [@scr4](https://boards.straightdope.com/u/scr4)\ **Post date:** [December 19, 2005, 7:57am UTC](https://boards.straightdope.com/t/could-early-man-only-see-three-colors/335129/11 "2005-12-19T07:57:53Z")
> [@Pleonast](#): > > So to detect light in a continuous manner, you’d need something analogous to the inner ear: an array of detectors, each tuned to a slightly different wavelength. This works well in the ear, because the each detector can sense or not the sound without attenuating signal. Is it possible to build something like this for light? It’s not hard to make a spectrograph out of organic materials. All you need is a focusing lens, a slit, a prism and an imaging detector (e.g. retina). But it will only make a spectrum along a slit. To get an image out of it, you need move this “eye” and scan across whatever you’re trying to see.