You may not like my answer, but the area of study which I think is relevant is art, and possibly physics, and the paint palette seems the best place to begin exploring. I also know that the alchemists tried mixing gold to paint. Also, different mediums give different effects, such as the translucence and the stained glass windows were a means of capturing light in unusual ways. I also see imagination as being extremely important, but I won't go any further, because I think that you specified the question of physics and physiology. So, while I am interested in imaginary colours through blending and even mixing effects such as ink and pencil, you may be more concerned with the actual making of the pigments, themselves rather than the exploration on paper. The creation of colours in the mind is interesting.

Hello Jack!

I really like your answer and thanks for replying. I didn't think about art but you are right. This topic is important in this debate. It is interesting how you recommended to me focus more in the colour itself (pigments) rather than how looks like in the paper. It is true and I am somehow agree that we have to purify the attributes of objects as empiricists said back in the day.
Also, I guess it is important to point out why the primary colours are cyan, magenta and yellow. Nevertheless, it blows my mind why is not green too. I think this pigment is so important and it is the main color of photosynthesis in plants...
Colours, as you said, are an interesting topic about philosophy, art, physics, physiology, etc...

Bearing in mind that you may be more interested in the physiology of imagination, the ideas of Oliver Sacks may be relevant for your discussion because he explores many kinds of unusual phenomena.

I am totally interested in the physiology of imagination. Oliver Sacks is relevant for this topic I guess because of all his researches about in his book awakenings but I am not so specialised in his works yet.

True purple, for which there seems to be no place in the physical spectrum, — javi2541997

... You mean, no corresponding light beam with a clear, single spectral peak? Each point (or strip) along the length of a rainbow produced by a glass prism, say, is reflecting such a beam. So the rainbow display is roughly analogous to a pure sine tone sweeping up in pitch through time. Stop the sweep at any moment and have a stable pitch, and that stable tone is roughly like a point (or strip) along the length of the rainbow.

On this analogy, purple is like a musical chord (or an ordinary non-pure tone from a violin, say). A light beam with more than one spectral peak in frequency. Real enough, then?

On this analogy, purple is like a musical chord. A light beam with more than one spectral peak in frequency. Real enough, then? — bongo fury

I understand your point and this metaphor you used is even beautiful in my opinion. It is literally like a musical chord. The light beam goes in the prism and then creates , as a frequency, the spectrum of light. Nevertheless, pointing out true purple or Violet, like you did, it is amazing how our eyes catch this reflection so I guess this is why is pure sensation or physiology because it creates an imaginary colour which is not related to the color wheel itself due to the lack of dependence for red and blue.
So... I guess we have also to focus in how light interferes in this shadows of colours.

is pure sensation or physiology — javi2541997

So not real enough?

Khaki is another example of a composite color that does not feature in the light spectrum, something the OP seems to call an imaginary colour if I understand well.

It's a colour name that English borrowed from Persian, in which it means: the colour of dirt (khak where kh is pronounced like the Spanish jota), of top soil. The original colour is any shade of light brown rather than dark green-brown, which is the tint for which we use the word khaki.

In Iran and Afghanistan, where Persian is spoken, there aren't many trees and greenery, often, so khaki is the dominant colour in the environment, the colour of the earth around you, and it deserves a name.

Blue in Persian is "abi", the colour of water (ab or aw).

So not real enough? — bongo fury

It is real enough :cheer:

Hello Oliver!

Thank you so much for sharing that example. I really like it. Fits completely what I was asking in the OP.

Khaki is another example of a composite color that does not feature in the light spectrum, — Olivier5

This is why is so interesting for sensations. Our eyes somehow, by the cones, receive the information of this colour but at the same time it doesn’t be part of the color wheel. so this why I guess we have to focus the attributes in a physiological path. But, I don’t want to criticise color wheel patters I guess it is important to at least put an order in terms of art.

In Iran and Afghanistan, where Persian is spoken, there aren't many trees and greenery, often, so khaki is the dominant colour in the environment, the colour of the earth around you, and it deserves a name.

Blue in Persian is "abi", the colour of water (ab or aw). — Olivier5

Probably Khaki is the primary colour in this specific zone of the Earth. It is interesting because it follows what I type previously about how important green due to nature, well better said, Khaki in Afganistán or Iran.

Again, thanks for sharing this example I will keep it in mind.

Thought you'd like it. :smile:

Thought you'd like it. :smile: — Olivier5

I did Oliver! :up: :100:

I have read some writing by Sacks but I am not sure if he has written on colours specifically. One thing I am aware of is that if I am feeling low, I feel that colours seem a bit wishy washy, whereas if I am feeling in great spirits, they seem to appear brighter.

The whole subject of seeing colour also falls into the area of ophthalmology. It seems to me that my mother sees colours differently since she had cataracts operated upon. To a large extent, visual perception of colour is dependent on the rods and cones and the retina, is part of the brain really. We know of people who are colour blind have severely altered sense of colour, but I wonder if we all see colours in exactly the same way generally, but this is probably an aspect which can be answered by neuroscientists.

However, the view of artists are probably relevant too. I remember it being so difficult to mix the exact shade of greens for certain leaves on trees. I think that there is plenty of khaki in the trees and I believe that camouflage, khaki designs was to enable soldiers to blend into the trees. Painting the sun in the sky is intricate too because one has to do it in such a way that the yellowish light does not blend with the blue to give a greenish effect. This is due to the way in which sun shows through the sky, but it is relevant to consideration of colour because objects often change shade by being seen through surfaces. Flouressent colour shades are interesting too, often created artificially, but they do create imaginary possibilities.

It is also interesting how the colour of blood changes from the blue of veins to red when a person bleeds, because oxygen comes into it. The colour of skin is interesting too because while people often speak of people being black or white, and of yellow as well, in actuality there is a whole multitude of shades and hues. Even within each of our bodies there are so many different areas of skin colour, mainly due to the thickness or thinness of skin in certain areas and blood flow variation.

It is also questionable if black is an actual colour. In some paint sets there is no black included because it is thought that it is possible to mix it from the other colours. When I tried this, I was not really satisfied with the result, because it didn't seem black enough. Another aspect arising when painting is the way the water gets discoloured by the dirty brushes, and as a child I used not to clean the brushes enough and this led to colours in the picture becoming a murky shade.

we all see colours in exactly the same way generally, but this is probably an aspect which can be answered by neuroscientists. — Jack Cummins

To be honest with you I think not. All the pigments are so unique but at the same time different towards our perception. It is true I am not a neuroscientist but I think it is clear how interpretive they are. This is beautiful and I think this is why art is so abstract depending of the people’s eyes.

It is also questionable if black is an actual colour. — Jack Cummins

This is interesting. We can argue it couldn’t be a true colour due to light prism doesn’t pass through it. I think black is there just to eliminate or cancel the develop of colours. We can say it is important because creates the feeling of diaphanous. Also when black is used in paints more than other colours tend to make the paint another feeling: sadness, nihilism, uncertainty, injustice p, etc... are somehow represented by black.

It's interesting to compare our colour categories with those of other cultures. You might like this but I read recently:

It may help us to realize the arbitrary character of
our own classifications if we study the very different
classifications of the same material which other
peoples have practised in the past or indeed still
practise in the present; for example, the way in
which the ancient Greeks and Romans classified
colours not as we classify them, by the qualitative
differences they show according to the places they
occupy in the spectrum, but by reference to some-
thing quite different from this, something connected
with dazzlingness or glintingness or gleamingness or
their opposites, so that a Greek will find it as natural
to call the sea ‘wine-looking’ as we to call it blue, and
a Roman will find it as natural to call a swan ‘scarlet’ —or the word we conventionally translate scarlet
— as we to call it white. It has been suggested that this
is because the Greeks and Romans were colour-blind.
But no sort of colour-blindness known to physiology
would account for the facts. In both languages there
are the rudiments of what we should call a true colour-
nomenclature ; and in both languages it happens
that there are words for red and green, the colours
that colour-blind persons cannot distinguish. — Colingwood, An Essay on Metaphysics

It's interesting to compare our colour categories with those of other cultures. You might like this but I read recently: — Olivier5

I just read the text you shared with me. It was so interesting. Probably I would never name the sea as “wine-looking” until today instead of blue.
Sometimes I think that colours have been used somehow as laws or patterns just to make an order. I guess this happens to try not make a chaos. If we see yellow it is just yellow doesn’t matter the our philosophical debate. This is just secondary for some people but I guess is beautiful debating about colours and its significance for us

I think you might like this brief of John Locke related to colours too:

If we block a child in a room all of his childhood teaching him the green colour while is actually yellow. Will he name all of his life “green” when he would actually see yellow? In this topic John Locke answered this is a perfect empirical experiment so he put the following sentence:
What you are trying to say is that complex terms like colours are not innate because we can teach children to misunderstand mixing them. I guess this is the same example of fearness. You can feel the fear because previously someone taught you what is darkness, witches, demons, etc... — John Locke

t (khak where kh is pronounced like the Spanish jota), — Olivier5

Yes I know! The concierge of my old school was called “Khalil” but we called him Jalil :smile:

The eye has certain receptors on the retina that detect color, the "cones." These come with three different sensitivities. Hence the three "primary" colors. — javi2541997

Well, not quite. Three receptor types do not imply three primary colors.

This might be the case if each receptor were sensitive to different parts of the spectrum like this:

Wikipedia: Young-Helmholtz theory

...but not if they highly overlap, like this:

Wikipedia: photopsin

In fact, I'm pretty sure you've seen a CIE-1931 chromaticity diagram before:

Wikipedia: CIE 1931 color space

Colors combine linearly on this chart (which only shows hue, not shades); your RGB monitor has three colors that are varied in intensity (and thus this diagram is only an approximation). An example of this can be found in the wiki SRGB article. So with three primaries, you can produce a color gamut that is a triangle. But the chart itself isn't a triangle; it's basically the color closure of all spectral colors, which forms that outside curve (the spectral locus). So, yes, we're trichromatic, but no, there aren't three primary colors... unless you pull tricks like CIE-1931 color space does, and make your primaries abstract.

True purple, for which there seems to be no place in the physical spectrum, is something we see when the cones sensitive to blue and red are both stimulated, giving us something like an imaginary color. — javi2541997

Are we not part of the physical world?

Opponent process color theory seems to explain colors pretty well. Current thought is that color opponent processes are explained by retinal mechanisms; in particular, retinal ganglion cells tend to mix signals from cones. There are three opponent color channels: a red-green channel, a yellow-blue channel, and a brightness channel. This is enough to make an axis... e.g., yellow-blue top-bottom, and green-red left-right. About the origin on this axis, you will find an entire color wheel. Purple is just what you see in the quadrant on the red portion of the green-red axis and the blue portion of the yellow-blue axis.

Slightly warp the color space I just described, and you just get the CIE-1931 chart again (since there's debate on the exact colors of color opponent processes, maybe it's less or more warping needed). On this warped diagram, the spectral colors are still forming that curve. It's not too surprising that there are colors outside of the curve, including those on the "line of purples". Color, as in that stuff we see and label with color labels, is a property of the human visual system. "Color" as in that property photons have is really nothing more than wavelengths (or frequencies, depending on your chosen unit), that happen to fall into a narrow band that the human visual system picks up, thereby producing those things we give color labels to. Either way, color per se isn't so much about photons per se as it is about how human eyes measure them, so I wouldn't try to put too much stock into the "colors" (human-color-label-things) that aren't wavelengths.

your RGB monitor has three colors that are varied in intensity (and thus this diagram is only an approximation). An example of this can be found in the wiki SRGB article. — InPitzotl

Hello InPitzotl!
Thank you for answering in my thread. I will check it out this articles later on :up:

So, yes, we're trichromatic, but no, there aren't three primary colors... unless you pull tricks like CIE-1931 color space does, and make your primaries abstract. — InPitzotl

Understandable. But I think in the past these colours were primary because somehow you could mixed them and then getting another variants. I guess this is why some artists or thinkers thought the Color Wheel was “primary”.
In this point, it is interesting how John Locke, despite it was centuries ago, tried to criticise the primary colours because of the reflection of the eye. This is why he wrote about Violet and how our cones in the eyes see it, etc...
So, the study of the colours not necessarily are provided by the spectrum of light but from a physiological point of view.

Either way, color per se isn't so much about photons per se as it is about how human eyes measure them, so I wouldn't try to put too much stock into the "colors" (human-color-label-things) that aren't wavelengths. — InPitzotl

Yes! Colours are human-label-things but... what happens with colourblindness people? We teach to them they are wrong because they do not see the basic patterns as we do. Thus, supposedly, the primary colours... so who is wrong here in terms of how our eyes reflect the colours we see?

The sky is blue because other wavelengths of light are filtered out by the atmosphere. I think of the perception of colour as the elimination of other wavelengths of light. Looking at the colour wheel (top) the violet is blocked by the red but emphasised by the blue.

Considering light as reflected from objects at the wavelength of the reflecting surface - again, wavelengths of light have been eliminated to convey to the eye the colour of the surface.

So then when we consider the organism - evolving in relation to a causal reality, and requiring reliable sensory information about the environment as a basis to make survival decisions - lest faulty perception be eliminated by natural selection, I'm inclined to assume that perception bears a very strong relation to objective reality - that colour exists objectively, and the subjective experience is accurate to reality.

Otherwise - how could we explain the overwhelming uniformity of perceptions that we can speak meaningfully of a blue sky?

Looking at the colour wheel (top) it does seem that the violet is blocked by the red but emphasised by the blue. — counterpunch

Interesting perception :100:

Otherwise - how could we explain the overwhelming uniformity of perceptions that we can speak meaningfully of a blue sky? — counterpunch

I guess this happens because of how we, the humans, always been tried of put an order or criteria. If most (not all) see the sea as blue due to the wavelengths from the sky, we established it as law of common reasoning because most of us literally see it that way. We cannot lead the people say it is “green” “white” or whatever because could be a chaos. Past thinkers used colours not only in art but as a way of showing how realty thus, physics, should work in our perceptions.
For example: you thought Violet is somehow emphasised by the blue, because this is how your eye told you. For me, as John Locke said, Violet is completely different pattern form the basics red/blue and this is why is important the cones of our eyes and how they interpret the reality itself.
Previously, this example was also shared:

so that a Greek will find it as natural
to call the sea ‘wine-looking’ as we to call it blue, and
a Roman will find it as natural to call a swan ‘scarlet’ —or the word we conventionally translate scarlet
— as we to call it white. It has been suggested that this
is because the Greeks and Romans were colour-blind.
But no sort of colour-blindness known to physiology
would account for the facts. In both languages there
are the rudiments of what we should call a true colour-
nomenclature ; and in both languages it happens
that there are words for red and green, the colours
that colour-blind persons cannot distinguish — An Essay On Metaphysics

I've read the Odyssey, and I'm fairly sure he speaks of the wine dark sea. But he also speaks of the gold and rosy fingers of dawn - which is an unerringly accurate description of colour. I think it's just poetic license; possibly describing the appearance of the Mediterranean ocean in moonlight, or maybe just evoking the idea of an ocean of wine. I don't think it literal; for while I was surprised to find the Odssey remains eminently readable 5,000 years after it was written, it is not literal. It's the grandfather of all sci-fi fantasy; magic and monsters on the high seas - 5,000 years ago, written as an epic poem.

Etymological evidence suggests the colour orange came into use quite recently; but I cannot therefore conclude that orange wavelengths of light were not reflected by orange things, before we agreed on a specific word for orange - and similarly I think "the wine dark sea" must have been a poetic phrase.

You haven't addressed at all the evolutionary argument I put forward; which is essentially that the organism has to be responsive and accurate to objective reality to survive. I think about fruit in the trees that goes red when it gets ripe. And it actually does. Fruit undergoes a chemical change, that then eliminates different wavelengths of light reflected from its surface - that signals to the organism that the fruit is ripe and ready to eat. Colour is not subjective - nor made possible by nomenclature. It exists in reality, as is then described in increasingly literal terms.

Fruit undergoes a chemical change, that then eliminates different wavelengths of light reflected from its surface - that signals to the organism that the fruit is ripe and ready to eat. Colour is not subjective - nor made possible by nomenclature. It exists in reality, as is then described in increasingly literal terms. — counterpunch

Yes I did understand your point about evolutionary argument but somehow I stuck in Violet perception...
we are agree that obviously colours exist in reality, thus, are objectively patterns. But this situation goes forward in terms of vocabulary and words. As you explained, when the fruit eliminates some wavelengths, it shows us the fruit is going to be ready to eat. But this is literally a good example of how we interpreted this natural objective pattern. You say we name it in literal terms but previously we had to be taught basic vocabulary to do so or at least interpret abstract things in object which are around us. Thus, the colours.
I guess this is why John Locke referred Violet as imaginary colour, but no for not existing in realty but literally the opposite. This is why he criticises the color wheel, when obviously the reflection which surpasses upon our cones it is an interpretation that could make us mistaken from the truest object of colour.
So, despite that could be so poetic speak about “wine dark sea” it shows how humans are subjective inside the objective. Some are poetic like Homero, others are more specific and scientific and wants to explain colours themselves, as the truly form. I guess both interpretation are cool and respectable.
This is why I still defend physiological is also important in terms of colour :up:

[img]http://

Nice image. It shows exactly what I mean. There are physical differences between wavelengths of light detected by the eye - albeit only across the narrow band of visible light. This is a feature of reality - we can know exists objectively and consistently, because it performs an evolutionary function. The fruit turns red. It stands out - attracts attention to the fruit in order to spread its seed. Thus logic dictates that colour is a consistent physical reality the human organism has evolved in relation to - and that different terms used to describe colours by ancient peoples, must be less specific language - rather than differences of perception.

In my view, construing colour as subjective in nature is a product of the "subjectivism industry" that characterises most of philosophy, religion, politics, the humanities, literature, culture. It is overwhelmingly the dominant paradigm; that since Descartes, in service to the Church, has rejected the profane physical world and seeks to accentuate the spiritual, through to the subjective. It's another form of heliocentrism; man putting man at the centre of reality - and it's a mistake.

I would rather assume the reality I perceive exists - if the fact you see it too isn't sufficient proof for the philosophical mind; then I must assume what I naturally assume everyday, and on that basis - recognise that reality is consistent in nature, and obeys physical laws that can be understood, and manipulated to therefore achieve freedom from the oppression of reality.

Art proves the essential similarity of perception for all people; the artist could not convey literal information to other people, across time - if reality were subjectively constructed by the individual. Yet art exists, and could not exist unless it were assumed that perception were objective in character, and similar to subsequent observers. Art is impossible to explain if reality is subjectively constructed. How can there be art, or traffic lights, or colour coded electrical wires, or fruit that signals ripeness as a reproductive strategy.

In my view, construing colour as subjective in nature is a product of the "subjectivism industry" that characterises most of philosophy, religion, politics, the humanities, literature, culture.

Interesting quote. I will check out more deeply this topic because it appears to be pretty cool.
We all are agree that somehow colours are built from a hard subjectivism or as you explained "subjectivism industry" point of view. Nevertheless, you also explained that:

Yet art exists, and could not exist unless it were assumed that perception were objective in character, and similar to subsequent observers. Art is impossible to explain if reality is subjectively constructed.

I guess it is not about impossibilities but how further our imagination can go when our eyes perceive the reality itself. This is why colours are an interesting topic inside philosophy not only physics. I respect of course, the spectrum of light we talked previously because is literally science explaining the development of colours when light is surpassing it, thus, the pure objective view.
Also, I defend that once we already understand how our reality works, I guess it is the turn of subjectivism because we humans tend to be so abstract too.
For example, imagine the rainbow, objectively we can say that is a curved band of different colours that appears in the sky when the sun shines through rain (Rainbow meaning )
But at the same time, we can philosophy about primary and secondary attributes too. So I guess in this point, colour depends on both: Pure objective and subjectivism.


[img]http://







It is interesting how violet goes directly in our eyes cones. John Locke was somehow right:smile:

You're right; it is pretty cool.

Thanks for participating in my thread! :100:

My pleasure. Thank you for affording me the opportunity to express my views.