# Colours, wavelengths, mixing of primaries

**URL:** <https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849>\
**Category:** Factual Questions\
**Created:** [November 15, 2002, 9:09am UTC](https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849 "2002-11-15T09:09:23Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![The\_Hamster\_King](https://avatars.discourse-cdn.com/v4/letter/t/8edcca/32.png) [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)\
**Post date:** [November 15, 2002, 6:39pm UTC](https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849/21 "2002-11-15T18:39:50Z")

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> [@](#):
>
> \*Originally posted by CalMeacham \*  
> \*\*  
> I don’t see why we couldn’t have been built with four-stimulus or five-stimulus eyes. I always thought it could make for an interesting science fiction story – the Aliens of Triskelion or wherever are upset with our color TV sets because our sets are tristumulus, but their eyes are quatrastimulus, and all our colors are “off”. \*\*

Adding more pigments to the eye does increase the number of colors you can distinguish but at some point you start to get diminishing returns. Three pigments are a big improvement over two, but four provides a much smaller improvement over three. From an evolutionary perspective the small increase in color discrimination provided by having more than three receptors probably isn’t worth the additional wiring required.

The problem with two receptors is that any color can be mimicked by a _single_ monochromatic source of the appropriate intensity. Two receptors are hardly better than one. It takes a minimum of three receptors to reliably distinguish different spectral distributions.

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**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\
**Post date:** [November 15, 2002, 7:21pm UTC](https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849/22 "2002-11-15T19:21:02Z")

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There was a thread around here a while ago about “tetrachromats”, people with four sets of colour receptors. Unfortunately, none of them were ultraviolet.

\<pause\> Here they are…

[Could Another Color Exist?](http://boards.straightdope.com/sdmb/showthread.php?threadid=114559)

[I see green. Do you see the same green?](http://boards.straightdope.com/sdmb/showthread.php?threadid=82318)

[Perfect senses?](http://boards.straightdope.com/sdmb/showthread.php?threadid=72788)

[I’m not a Tetrachromat. Please don’t ask me if your clothing matches.](http://boards.straightdope.com/sdmb/showthread.php?threadid=59802)

[Declare your mutation! Perhaps you could help save the world!](http://boards.straightdope.com/sdmb/showthread.php?threadid=48537)

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**Author:** ![MEBuckner](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mebuckner/32/2896_2.png) [@MEBuckner](https://boards.straightdope.com/u/MEBuckner)\
**Post date:** [November 15, 2002, 10:55pm UTC](https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849/23 "2002-11-15T22:55:35Z")

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I asked pretty much the same question a while back: [Question about color](http://boards.straightdope.com/sdmb/showthread.php?s=&threadid=49072). (Real informative thread title there, Buckner.)

Anyway, FWIW, you can go and read the responses on that thread, too.

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**Author:** ![wnorthr](https://avatars.discourse-cdn.com/v4/letter/w/ecccb3/32.png) [@wnorthr](https://boards.straightdope.com/u/wnorthr)\
**Post date:** [November 15, 2002, 11:25pm UTC](https://boards.straightdope.com/t/colours-wavelengths-mixing-of-primaries/136849/24 "2002-11-15T23:25:45Z")

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There’s an optics book called “Seeing the Light. Optics in Nature, Photography, Color, Vision and Holography.” by David Falk, Dieter Brill and David Stork published by Harper and Row in 1986 that is an excellent beginner’s book on optics.

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