<p>Usually, for something to be 'real', we want it in some reasonable manner to be objective or (because that is extremely vague) at least very consistent across subjective observers. Unfortunately, colour does not satisfy this.</p>

<ol>
<li><p><strong>Physical basis.</strong> As <a href="https://cogsci.stackexchange.com/a/4944/29">explained very well by @Stop_forgetting_my_account</a>: Physics does not have colour, it just has a continuous spectrum of wavelengths. Even when you look at the sensitivity of the 3 types of cones in the retina it is not discrete, but continuous. The categories of colours (i.e. "that's red", "that's blue") are produced by perception and these discrete-ish categories form the basis of colour <a href="http://plato.stanford.edu/entries/qualia/" rel="nofollow noreferrer">qualia</a>. Scientists can study these categories by asking participants if various stimuli feel like the same colour.</p></li>
<li><p><strong>Biological variation.</strong> As I mentioned in the previous point, most people have 3 types of cones, and a typical colour-matching experiment need 3 dials to tune a colour to be indistinguishable (by them) from one they see presented to them. However, there are colourblind individuals where 1 (or more) of the cone types are not expressed; such individuals only need two knobs to match a presented colour, and thus they will identify certain colours as the same though most people would experience them as different colours. Finally, there is the rare condition of <a href="https://en.wikipedia.org/wiki/Tetrachromacy" rel="nofollow noreferrer">tetrochromacy</a> (much more common among women than men) where an individual has 4 different types of cone cells. For most of these individuals, this does not result in being able to reliably distinguish colours that trichromats perceive as the same, and they are called non-functional tetrochromats. However, there have been <a href="http://www.dailymail.co.uk/health/article-2161402/Gabriele-Jordan-British-scientist-claims-woman-superhuman-vision.html" rel="nofollow noreferrer">reported cases of functional tetrochromats</a>; such individuals are able to reliably distinguish colours that would be identical to trichromats.</p></li>
<li><p><strong>Cross-cultural variation.</strong> Regier &amp; Kay (2009; see also reference within) discuss how these arbitrary boundaries between colours are language-dependent. Thus, the nuances of colour do not meet the psychological definition of a human universal even within people with the same biology.</p></li>
<li><p><strong>Intra-personal variation.</strong> The buck doesn't stop there. Gilbert and colleagues (2006) showed that the language dependence is supported in the right visual field (across from the 'language center' of the brain) but not the left. In other words, when I present colours in one part of your visual field, you experience them one way, and when I present them to the other, you then experience them in a fundamentally different way. This isn't an artifact of some physical property of your eyes, but of how your brain perceives colours (i.e. feedback from higher-order parts of the brain).</p></li>
</ol>

<hr>

<h2>Related posts and references</h2>

<ul>
<li><p><a href="https://cogsci.stackexchange.com/q/1364/29">Is it possible for certain people to perceive colors differently?</a></p></li>
<li><p><a href="https://cogsci.stackexchange.com/a/1317/29">Answer to "Is there a region of cortex which over a period of development becomes the seat of self?"</a></p></li>
<li><p>Gilbert, A. L., Regier, T., Kay, P., &amp; Ivry, R. B. (2006). <a href="http://dx.doi.org/10.1073/pnas.0509868103" rel="nofollow noreferrer">Whorf hypothesis is supported in the right visual field but not the left</a>. <em>Proceedings of the National Academy of Sciences of the United States of America, 103</em>(2), 489–494.</p></li>
<li><p>Regier, T., &amp; Kay, P. (2009). <a href="http://www.sciencedirect.com/science/article/pii/S1364661309001454" rel="nofollow noreferrer">Language, thought, and color: Whorf was half right</a>. <em>Trends in Cognitive Sciences, 13</em>(10), 439–446.</p></li>
</ul>

CC BY-SA 3.0
2014-02-10T21:25:34.133Z
I think you are stopping too early. The same person will perceive the same wavelength as two different colors depending on many other visual properties of the scene (e.g. color and luminance contrast to surrounding colors, texture of the colored object) and his own expectations of what color the object should be.
rumtscho
CC BY-SA 3.0
2013-11-13T06:23:07.037Z
2014-02-10T03:04:35.040Z
2017-04-13T12:56:16.417Z
Artem Kaznatcheev
<p>It appears that throughout your question you are touching on multiple questions and topics.  I will address them in a series of quotes and responses, beginning with the title:</p>

<blockquote>
  <p>Are colors real?</p>
</blockquote>

<p>They are not physical things.  Colors are a form of <em>perception</em> (an abstraction).  They exist in your head.  In physics the perception of colors is caused by light waves; a form of radiation.</p>

<blockquote>
  <p>We know that we distinguish colors when they fall on our photo
  receptors in our eyes and neurons pass its signals to our brain to
  recognise them as the specific colors.  How accurate is it?</p>
</blockquote>

<p>Color perception is subjective.  It is affected by all the matter that would affect the interpretation of colors - your eyes, nervous system, and brain.  Accuracy would require a benchmark to weigh relativity from.  How can you benchmark the difference between your perception of colors and something else's perception of color when there is no way to record how much somebody perceives color?  You cannot say that Bill sees this much redness, that much green, and 5% less purple than normal without a strong benchmark.</p>

<blockquote>
  <p>...There might be more colors than primary colors can
  make up which our eyes cant interpret it as a different color itself.</p>
</blockquote>

<p>Because colors are defined as combinations of light waves at certain frequencies, what you're suggesting is that there are more combinations of light waves than what humans can see - everything beyond the <a href="http://en.wikipedia.org/wiki/Visible_spectrum">visible light spectrum</a>.</p>

<blockquote>
  <p>My question is, is there any experiment which can tell us the color
  we see is the only and real color which is reflected by the object?</p>
</blockquote>

<p>There is only one actual color (aka combination of light waves) from a certain object that you will see at any given time.  If, however, you are asking if the color you perceive is the color you should perceive, then the answer is no.  You can't without a very strong benchmark to base your observations upon and a method for determining the accuracy of color interpretation in a given organism (because it requires a way to measure all the components that make up or affect perception)</p>

CC BY-SA 3.0
2014-02-10T13:56:50.777Z
_"You cannot say that Bill sees this much redness, that much green, and 5% less purple than normal without a strong benchmark."_ What about [tests for color perception](http://en.wikipedia.org/wiki/Color_perception_test)?
Steven Jeuris
CC BY-SA 3.0
2014-02-12T04:47:48.117Z
It's a relative measurement calibrated with what people normally see, and until normal has no error margin, you can't put a number in front of each color and say that it is an *absolute* measurement of perception.
kettlecrab
CC BY-SA 3.0
2014-02-01T23:23:04.297Z
Use common sense; this information can be found everywhere. That aside, I did link to Wikipedia, which is a citation as I am citing it.
kettlecrab
CC BY-SA 3.0
2013-11-10T08:24:10.400Z
2013-11-10T08:24:10.400Z
kettlecrab
<p>We know that we distinguish colors when they fall on our photo receptors in our eyes and neurons pass its signals to our brain to recognise them as the specific colors.  How accurate is it? For example, is there any experiment which can <em>measure</em> whether the color that we see is the real color that is reflected by that object? </p>

<p>I am thinking in terms of relativity. We might be interpreting a color red as red simply because our eyes and neurons and brain interpret it as red.  If this is the case there might be more colors than primary colors can make up which our eyes cant interpret it as a different color itself.</p>

<p>My question is, <strong>is there any experiment which can tell us the color we see is the only and real color which is reflected by the object?</strong></p>

CC BY-SA 3.0
2013-11-10T03:42:12.870Z
We've had this [before](http://physics.stackexchange.com/questions/77924/where-is-there-evidence-or-proof-that-colors-really-exist) (link required 10k rep), but it is deleted now, so I will copy the comment I made then: *"What is it with would-be philosophers who want physics to weigh in on the reality of things that people experience everyday? Frankly, the whole idea is silly. Color is the name we assign to the perception of different quality in light linked to the spectrum (rather than intensity) of the light."*
dmckee --- ex-moderator kitten
CC BY-SA 3.0
2013-11-10T04:22:16.027Z
Define "true color" as distinct form just plain ol' color and we might be able to tell you.
dmckee --- ex-moderator kitten
CC BY-SA 3.0
2013-11-10T05:19:05.670Z
Color is not a physical property it *is* perception. Frequency is a physical property, and while it is linked to the perceived color it is not uniquely linked. Even among humans the very range of frequencies that are visible varies a little; meaning that you can get two people in front of a spectrascope and find that only one of them can see a particular line. I was the one who couldn't.
dmckee --- ex-moderator kitten
<vision><sensation><color>
Are colors real?
Vaishakh Rajan K
# Are colors real?

(Asked by: username_0 on 2013-11-10)

We know that we distinguish colors when they fall on our photo receptors in our eyes and neurons pass its signals to our brain to recognise them as the specific colors. How accurate is it? For example, is there any experiment which can *measure* whether the color that we see is the real color that is reflected by that object?

I am thinking in terms of relativity. We might be interpreting a color red as red simply because our eyes and neurons and brain interpret it as red. If this is the case there might be more colors than primary colors can make up which our eyes cant interpret it as a different color itself.

My question is, **is there any experiment which can tell us the color we see is the only and real color which is reflected by the object?**

**Tags:** vision, sensation, color

> **Comments:**
> **username_1**: We've had this [before](http://physics.stackexchange.com/questions/77924/where-is-there-evidence-or-proof-that-colors-really-exist) (link required 10k rep), but it is deleted now, so I will copy the comment I made then: *"What is it with would-be philosophers who want physics to weigh in on the reality of things that people experience everyday? Frankly, the whole idea is silly. Color is the name we assign to the perception of different quality in light linked to the spectrum (rather than intensity) of the light."*  
> **username_1**: Define "true color" as distinct form just plain ol' color and we might be able to tell you.  
> **username_1**: Color is not a physical property it *is* perception. Frequency is a physical property, and while it is linked to the perceived color it is not uniquely linked. Even among humans the very range of frequencies that are visible varies a little; meaning that you can get two people in front of a spectrascope and find that only one of them can see a particular line. I was the one who couldn't.  

---

## 2 answers

### Answer by username_2 on 2013-11-13. Score: 13

Usually, for something to be 'real', we want it in some reasonable manner to be objective or (because that is extremely vague) at least very consistent across subjective observers. Unfortunately, colour does not satisfy this.

1. **Physical basis.** As [explained very well by @Stop\_forgetting\_my\_account](https://cogsci.stackexchange.com/a/4944/29): Physics does not have colour, it just has a continuous spectrum of wavelengths. Even when you look at the sensitivity of the 3 types of cones in the retina it is not discrete, but continuous. The categories of colours (i.e. "that's red", "that's blue") are produced by perception and these discrete-ish categories form the basis of colour [qualia](http://plato.stanford.edu/entries/qualia/). Scientists can study these categories by asking participants if various stimuli feel like the same colour.
2. **Biological variation.** As I mentioned in the previous point, most people have 3 types of cones, and a typical colour-matching experiment need 3 dials to tune a colour to be indistinguishable (by them) from one they see presented to them. However, there are colourblind individuals where 1 (or more) of the cone types are not expressed; such individuals only need two knobs to match a presented colour, and thus they will identify certain colours as the same though most people would experience them as different colours. Finally, there is the rare condition of [tetrochromacy](https://en.wikipedia.org/wiki/Tetrachromacy) (much more common among women than men) where an individual has 4 different types of cone cells. For most of these individuals, this does not result in being able to reliably distinguish colours that trichromats perceive as the same, and they are called non-functional tetrochromats. However, there have been [reported cases of functional tetrochromats](http://www.dailymail.co.uk/health/article-2161402/Gabriele-Jordan-British-scientist-claims-woman-superhuman-vision.html); such individuals are able to reliably distinguish colours that would be identical to trichromats.
3. **Cross-cultural variation.** Regier & Kay (2009; see also reference within) discuss how these arbitrary boundaries between colours are language-dependent. Thus, the nuances of colour do not meet the psychological definition of a human universal even within people with the same biology.
4. **Intra-personal variation.** The buck doesn't stop there. Gilbert and colleagues (2006) showed that the language dependence is supported in the right visual field (across from the 'language center' of the brain) but not the left. In other words, when I present colours in one part of your visual field, you experience them one way, and when I present them to the other, you then experience them in a fundamentally different way. This isn't an artifact of some physical property of your eyes, but of how your brain perceives colours (i.e. feedback from higher-order parts of the brain).

---

## Related posts and references

* [Is it possible for certain people to perceive colors differently?](https://cogsci.stackexchange.com/q/1364/29)
* [Answer to "Is there a region of cortex which over a period of development becomes the seat of self?"](https://cogsci.stackexchange.com/a/1317/29)
* Gilbert, A. L., Regier, T., Kay, P., & Ivry, R. B. (2006). [Whorf hypothesis is supported in the right visual field but not the left](http://dx.doi.org/10.1073/pnas.0509868103). *Proceedings of the National Academy of Sciences of the United States of America, 103*(2), 489–494.
* Regier, T., & Kay, P. (2009). [Language, thought, and color: Whorf was half right](http://www.sciencedirect.com/science/article/pii/S1364661309001454). *Trends in Cognitive Sciences, 13*(10), 439–446.

> **Comments:**
> **username_3**: I think you are stopping too early. The same person will perceive the same wavelength as two different colors depending on many other visual properties of the scene (e.g. color and luminance contrast to surrounding colors, texture of the colored object) and his own expectations of what color the object should be.  

---

### Answer by username_4 on 2013-11-10. Score: 7

It appears that throughout your question you are touching on multiple questions and topics. I will address them in a series of quotes and responses, beginning with the title:

> Are colors real?

They are not physical things. Colors are a form of *perception* (an abstraction). They exist in your head. In physics the perception of colors is caused by light waves; a form of radiation.

> We know that we distinguish colors when they fall on our photo
> receptors in our eyes and neurons pass its signals to our brain to
> recognise them as the specific colors. How accurate is it?

Color perception is subjective. It is affected by all the matter that would affect the interpretation of colors - your eyes, nervous system, and brain. Accuracy would require a benchmark to weigh relativity from. How can you benchmark the difference between your perception of colors and something else's perception of color when there is no way to record how much somebody perceives color? You cannot say that Bill sees this much redness, that much green, and 5% less purple than normal without a strong benchmark.

> ...There might be more colors than primary colors can
> make up which our eyes cant interpret it as a different color itself.

Because colors are defined as combinations of light waves at certain frequencies, what you're suggesting is that there are more combinations of light waves than what humans can see - everything beyond the [visible light spectrum](http://en.wikipedia.org/wiki/Visible_spectrum).

> My question is, is there any experiment which can tell us the color
> we see is the only and real color which is reflected by the object?

There is only one actual color (aka combination of light waves) from a certain object that you will see at any given time. If, however, you are asking if the color you perceive is the color you should perceive, then the answer is no. You can't without a very strong benchmark to base your observations upon and a method for determining the accuracy of color interpretation in a given organism (because it requires a way to measure all the components that make up or affect perception)

> **Comments:**
> **username_4**: Use common sense; this information can be found everywhere. That aside, I did link to Wikipedia, which is a citation as I am citing it.  
> **username_5**: _"You cannot say that Bill sees this much redness, that much green, and 5% less purple than normal without a strong benchmark."_ What about [tests for color perception](http://en.wikipedia.org/wiki/Color_perception_test)?  
> **username_4**: It's a relative measurement calibrated with what people normally see, and until normal has no error margin, you can't put a number in front of each color and say that it is an *absolute* measurement of perception.  

---

