# Why is there colour?
**URL:** https://boards.straightdope.com/t/why-is-there-colour/405849
**Category:** Factual Questions
**Created:** [May 29, 2007, 1:43am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849 "2007-05-29T01:43:53Z")
**Posts on this page:** 20
**Page:** 1
### Author:  [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)
#### Post date: [May 29, 2007, 1:43am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/1 "2007-05-29T01:43:53Z")
Maybe to _deep_ to ask here; but why is there colour? If all protons neutrons and electrons are all the same colour or colourless, why when they come together to form molecules they change?
virtually yours
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### Author:  [@Colibri](https://boards.straightdope.com/u/Colibri)
#### Post date: [May 29, 2007, 1:48am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/2 "2007-05-29T01:48:21Z")
Photons are what are “colored.” Specifically, light of different wavelengths is what we perceive as different colors. Color is a property of light, not of matter. Matter is perceived as being of different colors because of the wavelengths it reflects or transmits, versus what it absorbs.
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### Author:  [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)
#### Post date: [May 29, 2007, 2:09am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/3 "2007-05-29T02:09:52Z")
Color doesn’t really exist outside of our brains. It’s an arbitrary perception of various wavelengths of light. What determines the wavelengths we see from various objects is dependent upon electron structure, not protons or neutrons.
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### Author:  [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)
#### Post date: [May 29, 2007, 2:34am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/4 "2007-05-29T02:34:39Z")
And most objects that we see are colored differently, at least when illuminated by most light sources, because they reflect different wavelengths of light in different amounts.
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### Author:  [@Leaffan](https://boards.straightdope.com/u/Leaffan)
#### Post date: [May 29, 2007, 3:10am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/5 "2007-05-29T03:10:33Z")
Not to be belittling, but I think I learned this in grade 7.
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### Author:  [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)
#### Post date: [May 29, 2007, 3:13am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/6 "2007-05-29T03:13:29Z")
You need to read this Book: **The Physics and Chemistry of Color** by Kurt Nassau
> **[Amazon.com: The Physics and Chemistry of Color, 2nd Edition: 9780471391067:...](https://www.amazon.com/Physics-Chemistry-Color-2nd/dp/0471391069)**
>
> Amazon.com: The Physics and Chemistry of Color, 2nd Edition: 9780471391067: Nassau, Kurt: Books
For a quick answer, go here:
[http://webexhibits.org/causesofcolor/](http://webexhibits.org/causesofcolor/)
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### Author:  [@virtually\_yours](https://boards.straightdope.com/u/virtually_yours)
#### Post date: [May 29, 2007, 3:53am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/7 "2007-05-29T03:53:34Z")
[QUOTE=Leaffan]
Not to be belittling, but I think I learned this in grade 7.
[/QUOTE]
You learned and understood photons in grade seven? good for you. You’re not being belittling just insensitive. maybe I missd grade seven 🙂
virtually yours
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### Author:  [@Johanna](https://boards.straightdope.com/u/Johanna)
#### Post date: [May 29, 2007, 4:07am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/8 "2007-05-29T04:07:54Z")
[QUOTE=Q.E.D.]
Color doesn’t really exist outside of our brains. It’s an arbitrary perception of various wavelengths of light. What determines the wavelengths we see from various objects is dependent upon electron structure, not protons or neutrons.
[/QUOTE]
In addition: perception of colors somehow produced inside the brain like with LSD, without the optic nerve getting involved. Or pressure on the eyeball which produces perceptions of color called phosphenes. Or seeing colors in dreams.
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### Author:  [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)
#### Post date: [May 29, 2007, 4:20am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/9 "2007-05-29T04:20:16Z")
Electrons are behind the color you see. When a charge is accelerated (or decelerated sp?) it either absorbs or releases energy in the form of electromagnetic radiation. Light is a small portion of the electromagnetic spectrum. I will let the physicists deal with the specifics on that.
Most of the things you observe are chemicals. That means the electrons are usually (I’m not discussing metals) bound up in molecular orbitals. When a photon of visible (or slightly shorter than visible) wavelength hits a molecule it can do several things:
For many things, the photon simply hits an electron, the electron vibrates and reflects the photon unchanged. This is the reflected light that you see.
If the molecule has an empty molecular orbital that has the same energy as the photon + the energy of an orbital existing on the molecule, it can be absorbed. Once the energy is absorbed it can do several things.
The energy is usually released as heat, so nothing is seen in the visible spectrum.
Other times the excited electron can move to another molecular orbital releasing a new photon. This is called fluorescence. Glow in the dark stuff is a special type of fluorescence.
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### Author:  [@Nava](https://boards.straightdope.com/u/Nava)
#### Post date: [May 29, 2007, 6:25am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/10 "2007-05-29T06:25:28Z")
**Christopher** , everything is a chemical; just not necessarily a chemical compound.
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### Author:  [@Pasta](https://boards.straightdope.com/u/Pasta)
#### Post date: [May 29, 2007, 6:39am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/11 "2007-05-29T06:39:36Z")
[QUOTE=virtually yours]
If all protons neutrons and electrons are all … colourless, …
[/QUOTE]
Your choice of wording here makes me wonder: You didn’t happen to stumble upon the concept of “color” as pertaining to subatomic particles, did you? The clause “neutrons are colorless” is the kind of statement that would come up during a discussion of quark and gluon color, which (despite the use of the word “color”) has nothing to do with the color we see. If this has no relation to your question, then please disregard this post.
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### Author:  [@BrandonR](https://boards.straightdope.com/u/BrandonR)
#### Post date: [May 29, 2007, 6:40am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/12 "2007-05-29T06:40:51Z")
[QUOTE=Leaffan]
Not to be belittling, but I think I learned this in grade 7.
[/QUOTE]
My how you’ve contributed positively to this OP’s question.
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### Author:  [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)
#### Post date: [May 29, 2007, 7:51am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/13 "2007-05-29T07:51:33Z")
[QUOTE=Leaffan]
Not to be belittling, but I think I learned this in grade 7.
[/QUOTE]
How could your intent in saying this be anything _other_ than to be belittling? I thought it was a pretty fair question, and it got a succinct answer.
as a bit of a tangent off of the OP, I’m wondering now why color is relevant to us. Eventually, of course, organisms have adapted in response to perception of color with stuff like camouflage and mating rituals and “bright colors = poison” and all that happy stuff. But color recognition must have preceded all of this. Why would understanding the wavelength of energy bouncing off of an object be useful to an organism in this pre-color world?
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### Author:  [@Baffle](https://boards.straightdope.com/u/Baffle)
#### Post date: [May 29, 2007, 7:56am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/14 "2007-05-29T07:56:19Z")
Colour recognition is useful as a way to tell things apart. How can you tell one berry is ripe and the other is unripe from a distance? Of course we’re just perceiving the different wavelength reflected from the ripe strawberry’s chemicals compared to the unripe ones, but it’s certainly useful in knowing which berries to pick at now and which berries to leave alone for another week.
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### Author:  [@WoodenTaco](https://boards.straightdope.com/u/WoodenTaco)
#### Post date: [May 29, 2007, 8:06am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/15 "2007-05-29T08:06:41Z")
[QUOTE=Baffle]
Colour recognition is useful as a way to tell things apart. How can you tell one berry is ripe and the other is unripe from a distance? Of course we’re just perceiving the different wavelength reflected from the ripe strawberry’s chemicals compared to the unripe ones, but it’s certainly useful in knowing which berries to pick at now and which berries to leave alone for another week.
[/QUOTE]
That seems a bit chicken-and-egg-ish, to me. If I asked “Why do berries change color when they ripen?” I’m almost certain the overwhelming answer would be “So that animals will eat them at the proper time and distribute seeds more efficiently.”
The only things I can think of that would be distinguishable by color that wouldn’t fall victim to this chicken-and-the-egg problem are inorganic things, but I’m not aware of too many inorganic things that animals with eyes consume. Any help?
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### Author:  [@Baffle](https://boards.straightdope.com/u/Baffle)
#### Post date: [May 29, 2007, 8:50am UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/16 "2007-05-29T08:50:10Z")
“The only rock we eat is salt.”
Or so I’m always told.
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### Author:  [@Chief\_Pedant](https://boards.straightdope.com/u/Chief_Pedant)
#### Post date: [May 29, 2007, 12:04pm UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/17 "2007-05-29T12:04:03Z")
[QUOTE=Leaffan]
Not to be belittling, but I think I learned this in grade 7.
[/QUOTE]
Amazing. There is so much wrapped up in the question that to understand it in 7th grade is phenomenal.
We could start with “What is light?” and move into “How does the brain perceive color?” for starters.
I always try to remember that there are no stupid questions. There are only stupid people. If I ask why an apple falls, I’m probably just stupid. If Newton asks the same question, it’s not likely he would be satisfied with the 7th grade answer.
Absent knowing who the questioner is and what depth he’s looking for, the phrasing of your answer suggests it’s a 7th grade level answer. And that is belittling.
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### Author:  [@Nava](https://boards.straightdope.com/u/Nava)
#### Post date: [May 29, 2007, 12:24pm UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/18 "2007-05-29T12:24:15Z")
Re. berries.
Color (understood not as “this is blue” and “this is red” but as “wavelengths of light”) existed waaaaay before color recognition. The visible and near-IR spectrum (visible to other earth species) happen to be the part of the light spectrum that carry most information about chemical composition. Vision evolved (trying) to make the best possible use of what the laws of physics were already doing.
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### Author:  [@WarmNPrickly](https://boards.straightdope.com/u/WarmNPrickly)
#### Post date: [May 29, 2007, 1:23pm UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/19 "2007-05-29T13:23:44Z")
> [@](#):
>
> Christopher, everything is a chemical; just not necessarily a chemical compound.
I would not consider a plasma to be a chemical. But a plasma certainly produces light.
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### Author:  [@Johanna](https://boards.straightdope.com/u/Johanna)
#### Post date: [May 29, 2007, 2:23pm UTC](https://boards.straightdope.com/t/why-is-there-colour/405849/20 "2007-05-29T14:23:39Z")
[QUOTE=Nava]
Re. berries.
Color (understood not as “this is blue” and “this is red” but as “wavelengths of light”) existed waaaaay before color recognition. The visible and near-IR spectrum (visible to other earth species) happen to be the part of the light spectrum that carry most information about chemical composition. Vision evolved (trying) to make the best possible use of what the laws of physics were already doing.
[/QUOTE]
That is one of the coolest science answers I’ve ever seen here. You should be the next Cecil.
edit:
Cecelia.
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