Why Red, Blue, Yellow and... Green?

[Flickerdart]

Originally Posted by sktarq

And this is totally training. I went to a high school with a museum of paleontology on campus. White sand stone was just a white sand stone when I started but by the time I left it was a dozen microshade. And if you look at the field notes of most paleontologist to describe how to find the exact point where the fossil was removed the descriptions include blues, greens, purples, oranges, umber etc o- all to describe a mass of stone that most people would call grey. That adjusted vision is still with me today. But only with plants and earth materials.

That sounds exactly like stonecunning.

[Elemental]

Originally Posted by Mauve Shirt

I always thought they should take ugly yellow out of the crayon box and add more purple.

I am in complete agreement with you concerning this. With all the space wasted on the colours that aren't nice, they could add more nice colours!

[Heliomance]

True, that's a factor I hadn't taken into account. I don't imagine that effect would come into play with the color circles they were using, though.

[Wardog]

Another thing to consider: how we name colours depends on context.

"White" people are usually pink or pinky-brown.
"White" grapes are green.
"White" wine is greeny-yellow.


Also, how we percieve colour also depends on what other colours and shades we see with them, as in this optical illusion:
http://www.popularscience.co.uk/?p=1478

[Mauve Shirt]

Originally Posted by Wardog

"White" people are usually pink or pinky-brown.

Unless they play minecraft and/or work in a basement and/or are Scandinavian. Then they're so white they're practically luminescent!

[GrlumpTheElder]

Originally Posted by sktarq

Grlump: I remember from MY Psych 101 book that they described a tetrachrome as the basic human eye with two kinds of cone one that was responsible for red (with a positive reaction) and green (with a negative reaction-or impeeded reaction I forget the exact term in the last 13 years) and a second type of cone with a blue (with a positive reaction) and a yellow (the opposite).

I think you meant two cone systems rather than just cones (see Trog's link to Opponent Coding Processes). Opponent Process is the reason we can't perceive a reddish-green or a blueish-yellow. To account for the opponent-appearance of colours there are two chromatic (red-green and blue-yellow) opponent systems and one achromatic (black-white) opponent system.The first stage of colour vision is trichromatic (involving three types of detectors at the photoreceptor stage) and the second stage involves these three opponent processes.
The image below should help:

From http://www.visualexpert.com/

As a key, L stands for Long Wavelenth Light, or red. M stands for Medium Wavelength, or green. S stands for Short Wavelength, or blue.

Ignore the first system.
If the eye is exposed to red light for a period of time, the red receptor (L) will become fatigued. Then, if white light is presented, the white light will appear green.

As there is no receptor for yellow, it is substituted with a red/green system. The same applies. If the eye is exposed to blue light for a period of time, the blue receptor (S) will become fatigued. Then, if white light is presented, the white light will appear yellow.

Originally Posted by sktarq

Red Green colour blindness was due a failure in the first type of cone. They also presented the yellow reaction as being rather new to science. Why was it presented in this way? A book that thought that psych 101 students couldn't get it? was it thought that this was true for a few years in the late 90's?

There are many different types of colour deficiency (only one true type of colour blindness). By Red/Green colour blindness, you can either mean Dichromacy or Anomalous trichromacy. Dichromacy is when you are missing a certain cone (protanopia is the lack of a L cone (red) and deuteranopia is lack of a M cone (green)). Anomalous trichromacy is when the sensitivity of a certain cone is not at usual parameters (protanomaly is when the L cone is shifted towards the M cone and deuteranomaly is when the M cone is shifted towards the M cone.)

In the 90s there were a lot of new theories presented as fact that have now been disproved.

Originally Posted by Ravens_cry

Not sure, I've never tried it, but I have noticed things look a little bluer with MY right eye compared to MY left.

The main reason this happens is that one eye is slightly adapted to certain wavelengths of light. In the average situation, you're not getting exactly the same light in both eyes. As with above, it's possible that when you noticed this, the light entering your right eye had been more yellow, fatiguing the R/G system in that eye and causing white light to appear bluer. It's not permanent though. I had the same thing happen to me quite a lot, because of where MY window was in MY room. One eye got different light levels, resulting in the different appearances of a white surface...

I think that's everything.

tl:dr
The neural system of vision is funky!

[WalkingTarget]

Originally Posted by Tvtyrant

This thread is a little long to read all the way through, but there was a book that analyzed the Homeric epics and came to the conclusion that the ancient Greeks had not yet begun to distinguish between colors. Instead the book posits that they concentrated on intensity, using examples like a comparison of iron and cows to show something dull.

William Gladstone, on-again off-again British Prime Minister, advanced a theory in the 1850's that Greeks of Homer's time (and I think people in general using Homer's text as just a source text) hadn't developed/were only then developing color vision due to the things you point out. That's pretty much discounted these days, more accepting that they simply had grouped colors by intensity/saturation rather than specific frequencies.

Guy Deutscher's Through the Language Glass discusses this and other color/thought-process/perception crossovers. I found it interesting. One of my favorite bits was how the language that was the source of the word "kangaroo" has no relative directional words (left, right, front, behind, etc.) - they use the equivalent of cardinal directions for everything.

[sktarq]

Originally Posted by GrlumpTheElder

I think you meant two cone systems rather than just cones (see Trog's link to Opponent Coding Processes). ...In the 90s there were a lot of new theories presented as fact that have now been disproved.
...I think that's everything...The neural system of vision are funky!

Thanx it seems like some sort of version of this is what they were trying to get accross. Though they did not present it a cone systems. (They had a picture of two cones on the movie screen-one for red/green and one for blue/yellow) I'm going to put that down to it being a psych class not anatomy or vision science. Thank you for that explination.

[nedz]

Originally Posted by Ravens_cry

That sounds frankly absurd given the mention of colour in contemporary and older works.
The language of the time may have lacked specific words, but even English doesn't name *all* the colours.

Pink wasn't named until the 17th Century, and even then it was yellow.

Originally Posted by willpell

Silly heck, I'd pay good money for luminous color paint that you could use to create instant vanity flashlights at a rave or something.

Glowstick, Snip, Paint.
Its a little bit toxic though.

[Devils_Advocate]

Originally Posted by Heliomance

What else would you call it? Seems pretty cultural to me.

"Individual capability", I guess? I think of the word "culture" as referring to how people interact with each other. By which standard the language difference itself is the cultural element, and color discrimination is the related not inherently cultural thingy.

That I did not know, and it's fascinating. I am tempted to drop a [citation needed] on you though.

There's a link to a relevant paper underneath the comic. Though I haven't read it myself.

(Dinosaur Comics! Where dinosaurs discuss linguistics, complete with references! Sometimes!)

Eh, that's correctable for.

How? What would it even mean to "correct for" this?

The point is not an important one - the point is that, whether we decide to use frequency or wavelength, we do have a quantitative way to describe colour.

The point? I do believe you mean your point, Heliomance. And yeah, I GOT THAT. To which I responded with my own point: We have more than one quantitative way to describe color, and a pair of colors could be called "more similar" or "less similar" to each other than another pair of colors depending on how the difference between them is quantified! That's what I meant when I said "I'm not sure that there's an unbiased measure of 'similarity' in this context."

The two measures will not consistently produce identical results! How is that not important?

I'm allowed to suspect whatever I want to suspect. That's what a hypothesis is. It remains a hypothesis until either disproved or sufficient supporting evidence is obtained.

I'm not talking about what's allowed, I'm talking about what's rational. And there are degrees of suspicion, quantifiable as probability estimates. When you receive evidence for or against a hypothesis, you should consequently regard it as more or less probable. (Bayes' theorem is the relevant formal mathematics.) Hypotheses can't be empirically "proved" or "disproved"; it's just that the probabilities we assign to them just get driven near to 0% or 100%. But "near" is relative, not absolute.

(Assigning a theory a probability of exactly 0% or 100% means planning to never interpret further evidence as contradicting what you presently believe, no matter what you observe. At which point you've abandoned empiricism with regard to that particular issue.)

Originally Posted by Watcher

EDIT: Whoah, I looked at the stoplight photos, and they all do seem to be bluish instead of green! It could be like how embers look purple through some cameras but red to people looking at them. I'll look at the stoplights on my way to the city tomorrow.

EDIT 2: Nopers. All of the stoplights are completely green. Some of the green arrows have a hint of bluish in them, but there aren't any blue or even tealish lights. Maybe it's the cameras. Maybe other places have blue lights and there just aren't any in this city.

Looking at stoplights as I've walked around, I've found that some of them are at least close to cyan whereas others really are decidedly green. It seems that there can be considerable variation between the lights even in a relatively small area, sometimes.

Originally Posted by Wardog

"White" people are usually pink or pinky-brown.

More of a peach; that is to say, a light orangish color. Whereas "black" people are brown, i.e. ... a dark orangish color.

Human skin doesn't really vary much in hue.

[Heliomance]

Originally Posted by Devils_Advocate

How? What would it even mean to "correct for" this?

The easiest way would be to measure both frequency and wavelength, and see if it's even an issue with the colours used. It could well be that there isn't a problem with those specific colours, that wavelength and frequency agree. If not, well, I'm sure someone somewhere has done an official scale of colour similarity. Hmm, this looks relevant. Bit dense for me, though.

Originally Posted by Devils_Advocate

I'm not talking about what's allowed, I'm talking about what's rational. And there are degrees of suspicion, quantifiable as probability estimates. When you receive evidence for or against a hypothesis, you should consequently regard it as more or less probable. (Bayes' theorem is the relevant formal mathematics.) Hypotheses can't be empirically "proved" or "disproved"; it's just that the probabilities we assign to them just get driven near to 0% or 100%. But "near" is relative, not absolute.

(Assigning a theory a probability of exactly 0% or 100% means planning to never interpret further evidence as contradicting what you presently believe, no matter what you observe. At which point you've abandoned empiricism with regard to that particular issue.)

It's quite easy to disprove a hypothesis, all you need is a single counterexample. Regardless, as neither of us have actually presented any new concrete evidence, I've not had anything to modify my hypothesis probabilities with. The paper I linked above might well answer the question; unffortunately I can't understand it.

[nedz]

Originally Posted by Heliomance

The easiest way would be to measure both frequency and wavelength, and see if it's even an issue with the colours used. It could well be that there isn't a problem with those specific colours, that wavelength and frequency agree. ...

Erm, for any wave: v = f λ
where v is velocity, f is frequency and λ wavelength.
For light v = c, which in any given medium is a constant.

So
if you measure f you know λ, because λ = c / f
also if you measure λ then you know f, because f = c / λ

Does this help ?

[Devils_Advocate]

Originally Posted by Heliomance

The easiest way would be to measure both frequency and wavelength, and see if it's even an issue with the colours used. It could well be that there isn't a problem with those specific colours, that wavelength and frequency agree.

Even so, I have little doubt that one could devise some third scale that would "disagree with" both. My point is that the scale chosen matters.

Treating similarity as something that you can measure means taking something you can measure and calling it "similarity". But this is simply playing games with language, is it not?

If not, well, I'm sure someone somewhere has done an official scale of colour similarity.

Official does not equal non-arbitrary.

Hmm, this looks relevant. Bit dense for me, though.

Sounds like an attempt to explain color perception and maybe to quantify how similar colors appear to be to human observers, which is basically the opposite of what you want.

It's quite easy to disprove a hypothesis, all you need is a single counterexample.

Once you've certainly got a counterexample you've certainly disproved the hypothesis, but how can you justify certainty in the counterexample? Infinite regress, problem of induction, etc.

Furthermore, probabilistic hypotheses -- e.g. "This coin will come up tails half of the times it's flipped" -- don't really have counterexamples.

Regardless, as neither of us have actually presented any new concrete evidence, I've not had anything to modify my hypothesis probabilities with.

But evidence doesn't need to be concrete to be for or against a proposition, does it? I'll admit that I'm not really familiar with the meaning of "concrete" in this context.

Originally Posted by nedz

Erm, for any wave: v = f λ
where v is velocity, f is frequency and λ wavelength.
For light v = c, which in any given medium is a constant.

So
if you measure f you know λ, because λ = c / f
also if you measure λ then you know f, because f = c / λ

Does this help ?

Nope!

Originally Posted by Devils_Advocate

X - Y is not directly proportional to c/X - c/Y; you cannot multiply one of those expression by a constant to get the other. As I said, you can even see this in Erloas's graph. Violet light covers a larger range of frequencies than red light but a smaller range of wavelengths.

[nedz]

Going back to the OP

The Romans and Byzantines used Red, White, Green and Blue for their chariot racing.

Maybe they didn't have Yellow paint ?

[Heliomance]

Originally Posted by Devils_Advocate

Sounds like an attempt to explain color perception and maybe to quantify how similar colors appear to be to human observers, which is basically the opposite of what you want.

If actual sound evidence can be found that contradicts my hypothesis, I will naturally abandon it - that's how science works. You have not provided any.

[Artemis97]

Just came across this while watching Netflix. I thought it was appropriate to this conversation and that you folks might find it interesting. Enjoy!