# Colors and Rainbows **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [January 28, 2011, 11:15am UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289 "2011-01-28T11:15:30Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![djinteractive](https://avatars.discourse-cdn.com/v4/letter/d/b4bc9f/32.png) [@djinteractive](https://boards.straightdope.com/u/djinteractive)\ **Post date:** [January 28, 2011, 11:15am UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/1 "2011-01-28T11:15:30Z")
[http://www.straightdope.com/columns/read/449/could-early-man-only-see-three-colors](http://www.straightdope.com/columns/read/449/could-early-man-only-see-three-colors) In Cecil’s column he states “Yet an American describing it will list the hues as red, orange, yellow, green, blue, purple, or something of the kind.” Minus possibly indigenous people, doesn’t almost any other culture describe 6 or 7 (indigo) colors? Is an an optical illusion that rainbows seem to have specific colors that are in a wider band than other colors that we think of as red, blue, green etc. It seems as if the differences in wavelength should be free flowing from one color to the next like on a computer but when I picture and think of a rainbow I see these color differences. It is just what we were thought or is there a specific reason we see these exact colors as being the “actual” color. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 28, 2011, 2:26pm UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/2 "2011-01-28T14:26:25Z")
i don’t know about other cultures, but there’s nothing ironclad about the choices of color. You could as easily see orange as merely the shading from yellow to red, rather than as a separate color. You could lump blue, indigo, and violet together as one lump. Or you can split red up into a variety of shades of red. Physicists essentially split colors up into an infinite number of wavelengths. the colors certainly aren’t chosen because they are equally wide bands within the rainbow (or as generated by a prism). Yellow takes up a surprisingly small portion of a prismatic or diffraction grating spectrum relative to the broad band that is red. And not all rainbows are the same. As the size of the drop forming the rainbow changes, so do the widths of the colors\*. With extremely small mist drops, the rainbow can be completely white. As the drops get larger, different colors appear, but for some sizes, some colors will be negligible or completely absent. M. Minnaert, in his clasic book **the Nature of light and Colour in the Open Air** gives a chart that allows you to determine the sizes of the drops making up the bow, based upon the relative sizes of the different colored bands. \*In a perfect geometrical optics rainbow, the widths of thew different color bands ought to be identical, independent of the size of the drops. The variation of the appearance of the rainbow with the sizes of the drops is thus a powerful argument for the wave nature of light, and it’s one that Thomas Young (of Young’s slit experiment fame) made on behalf of the Wave Theory of Light. ---
**Author:** ![glowacks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/glowacks/32/5548_2.png) [@glowacks](https://boards.straightdope.com/u/glowacks)\ **Post date:** [January 28, 2011, 4:26pm UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/3 "2011-01-28T16:26:11Z")
> [@djinteractive](#): > > [http://www.straightdope.com/columns/read/449/could-early-man-only-see-three-colors](http://www.straightdope.com/columns/read/449/could-early-man-only-see-three-colors) > > In Cecil’s column he states “Yet an American describing it will list the hues as red, orange, yellow, green, blue, purple, or something of the kind.” > > Minus possibly indigenous people, doesn’t almost any other culture describe 6 or 7 (indigo) colors? > Is an an optical illusion that rainbows seem to have specific colors that are in a wider band than other colors that we think of as red, blue, green etc. It seems as if the differences in wavelength should be free flowing from one color to the next like on a computer but when I picture and think of a rainbow I see these color differences. It is just what we were thought or is there a specific reason we see these exact colors as being the “actual” color. ## Indigo and violet were differentiated because Newton wanted a 7th color into the rainbow; he wanted to link the rainbow to all other mystical occurrences of sets of size 7. I don’t find indigo to be nearly as basic a color word as red, orange, yellow, green or blue; indigo and violet are both “purple” to me. Looking at a reproduction of a rainbow I can readily distinguish areas of the first five and an area of purple, but have no idea where one would separate violet from indigo. Part of this may be conditioning, and certainly some parts are wider than others, but I have definite basic words for 6 of the colors there, not 7. The Russian language is somewhat unusual in that it has unrelated color terms of “light blue” and “dark blue”, although I don’t know if it’s the same kind of difference between pink and red or whether they’re separate spectral colors. ---
**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:** [January 28, 2011, 4:47pm UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/4 "2011-01-28T16:47:11Z")
It may be partially arbitrary, but the nature of normal color vision in humans is a key factor. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 28, 2011, 5:32pm UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/5 "2011-01-28T17:32:31Z")
> [@](#): > > Indigo and violet were differentiated because Newton wanted a 7th color into the rainbow; he wanted to link the rainbow to all other mystical occurrences of sets of size 7. It’s not entirely “mystical” As I say in the thread on **Colors** : > [@](#): > > If you read his Optics, Newton was clearly drawing an analogy between the tones of music and the colors of the spectrum\*. His choice of seven colors was thus drawn from the seven notes in an octave (rejecting the one at the top of the octave – Red Orange Yellow Green Blue Indigo Violet was the Do Re Mi Fa Sol La Ti of the visible scale. > **[Colors](https://boards.straightdope.com/sdmb/showthread.php?t=594463)** > > In grade school in the '30s I was taught the seven colors of the rainbow through the mnemonic name Roy G. Biv. Start with these and add a couple for brown and gray (grey in Cecil’s column) and you get about nine as a basis on which to build - though... ---
**Author:** ![Powers](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Powers](https://boards.straightdope.com/u/Powers)\ **Post date:** [January 29, 2011, 2:35pm UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/6 "2011-01-29T14:35:13Z")
> [@CalMeacham](#): > > \*In a perfect geometrical optics rainbow, the widths of thew different color bands ought to be identical, independent of the size of the drops. Yes, mathematically, but not perceptually. A broader range of wavelengths is usually seen as “green” to human eyes than for other colors, so the green band should appear wider than the yellow band regardless of optics. Powers &8^] ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [January 30, 2011, 1:27am UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/7 "2011-01-30T01:27:34Z")
> [@](#): > > Yes, mathematically, but not perceptually. A broader range of wavelengths is usually seen as “green” to human eyes than for other colors, so the green band should appear wider than the yellow band regardless of optics. You completely misunderstand what I was saying. The statement indicates that the appearance of the rainbow, in the geometrical optics limit, is independent of drop size, _not_ that the colors ought to have the same width (which is what you appear to think is what I mean). ---
**Author:** ![Wendell\_Wagner](https://avatars.discourse-cdn.com/v4/letter/w/8491ac/32.png) [@Wendell\_Wagner](https://boards.straightdope.com/u/Wendell_Wagner)\ **Post date:** [January 30, 2011, 1:38am UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/8 "2011-01-30T01:38:59Z")
There are a large number of different ways that languages distinguish color: > **[Linguistic relativity and the color naming debate](https://en.wikipedia.org/wiki/Linguistic_relativity_and_the_color_naming_debate)** > > The concept of linguistic relativity concerns the relationship between language and thought, specifically whether language influences thought, and, if so, how. This question has led to research in multiple disciplines—including anthropology, cognitive science, linguistics, and philosophy. Among the most debated theories in this area of work is the Sapir–Whorf hypothesis. This theory states that the language a person speaks will affect the way that this person thinks. The theory varies between It’s not remotely true that all languages see six or seven colors in the rainbow. ---
**Author:** ![Powers](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Powers](https://boards.straightdope.com/u/Powers)\ **Post date:** [February 1, 2011, 2:42am UTC](https://boards.straightdope.com/t/colors-and-rainbows/569289/9 "2011-02-01T02:42:20Z")
> [@CalMeacham](#): > > You completely misunderstand what I was saying. > > The statement indicates that the appearance of the rainbow, in the geometrical optics limit, is independent of drop size, _not_ that the colors ought to have the same width (which is what you appear to think is what I mean). Apologies. Powers &8^]