How many color bands in the rainbow?

All my old optical textbooks break up the rainbow into six colors bands. (Red, Orange, Yellow, Green, Blue, Violet)

The familiar picture of a prism on the Pink Floyd's The Dark Side of the Moon also depicts six color bands (from 1973).

However, I see on Wikipedia the assignment of seven color bands. (Red, Orange, Yellow, Green, Cyan, Blue, Violet)

Visible spectrum - Wikipedia

I am looking at my Dark Side of the Moon album cover and the color between green and violet looks blue (and a very lovely blue too I might add), whereas when I pull up an image on it on my computer monitor, what I see in between green and violet looks like cyan.

Is the assignment of seven color bands in the spectrum becoming an accepted system? Maybe driven by the increasing use of electronic displays?

I have been using blue and cyan optical filters for my entire career, and navigating the worlds of additive and subtractive colors with clarity of communication with other professionals. But is there shift going on in terminology that I need to keep up with?

(edit: within five minutes of posting this I got three advertisements on my web browser for cyan house paints. make of that what you will)

I wonder if this may be due to a recent increase in interest about colours between blue and green and where each person draws the boundary.

This test seems to have been doing the rounds recently. It aims to find where you draw the line between blue and green. The "About" page on that website makes interesting reading.

OpticsEngineer said:

All my old optical textbooks break up the rainbow into six colors bands. (Red, Orange, Yellow, Green, Blue, Violet)

The familiar picture of a prism on the Pink Floyd's The Dark Side of the Moon also depicts six color bands (from 1973).

However, I see on Wikipedia the assignment of seven color bands. (Red, Orange, Yellow, Green, Cyan, Blue, Violet)

Visible spectrum - Wikipedia

I am looking at my Dark Side of the Moon album cover and the color between green and violet looks blue (and a very lovely blue too I might add), whereas when I pull up an image on it on my computer monitor, what I see in between green and violet looks like cyan.

Is the assignment of seven color bands in the spectrum becoming an accepted system? Maybe driven by the increasing use of electronic displays?

I have been using blue and cyan optical filters for my entire career, and navigating the worlds of additive and subtractive colors with clarity of communication with other professionals. But is there shift going on in terminology that I need to keep up with?

(edit: within five minutes of posting this I got three advertisements on my web browser for cyan house paints. make of that what you will)

Click to expand...

From my school days a very long time ago, I remember ROYGBIV,, which includes Indigo in the colours.

Wikipedia advises as follows:

ROYGBIV is an acronym for the sequence of hues commonly described as making up a rainbow: red, orange, yellow, green, blue, indigo, and violet. There are several mnemonics that can be used for remembering this color sequence, such as the name "Roy G. Biv" or sentences such as "Richard of York Gave Battle in Vain".

How long ago did you buy the album?

--

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Tom Axford said:

This test seems to have been doing the rounds recently.

Click to expand...

Thanks! This can solve a dispute with my wife about what is green, what is blue...
I was not in the midle ;-)

Ruud

OpticsEngineer said:

All my old optical textbooks break up the rainbow into six colors bands. (Red, Orange, Yellow, Green, Blue, Violet)

The familiar picture of a prism on the Pink Floyd's The Dark Side of the Moon also depicts six color bands (from 1973).

However, I see on Wikipedia the assignment of seven color bands. (Red, Orange, Yellow, Green, Cyan, Blue, Violet)

Visible spectrum - Wikipedia

I am looking at my Dark Side of the Moon album cover and the color between green and violet looks blue (and a very lovely blue too I might add), whereas when I pull up an image on it on my computer monitor, what I see in between green and violet looks like cyan.

Is the assignment of seven color bands in the spectrum becoming an accepted system? Maybe driven by the increasing use of electronic displays?

I have been using blue and cyan optical filters for my entire career, and navigating the worlds of additive and subtractive colors with clarity of communication with other professionals. But is there shift going on in terminology that I need to keep up with?

(edit: within five minutes of posting this I got three advertisements on my web browser for cyan house paints. make of that what you will)

Click to expand...

For the younger generation (Grandson), there's a slightly different mix of colours:

Red Dinosaur; Orange Dinosaur; Yellow Dinosaur; Green Dinosaur; Blue Dinosaur; and Purple Dinosaur!



--
DaveR

Thanks for the interesting link.

It is telling that with his Phd in neuroscience in 2014, he is forcing the choice of blue or green and not allowing for an intermediate zone of cyan as Wikipedia suggests.

When I look at sunlight coming through a prism and projecting colors on the wall across the room, I judge there is a narrow band of cyan. But it is very narrow (in terms of how many millimeters it is taking on the wall as compared to green and blue.)

As far as the test at the link....

On my iPhone I judged the colors to pick the dividing line as 93% bluer than most people

On my Dell computer monitor, I was greener than 66% of most people.

Interesting graphic

six colors of dinosaurs. but seven colors in the rainbow.

Ruud uit de Graaf said:

Tom Axford said:

This test seems to have been doing the rounds recently.

Click to expand...

Thanks! This can solve a dispute with my wife about what is green, what is blue...
I was not in the midle ;-)

Ruud

Click to expand...

Surely this makes little sense.

It is using some words, namely blue and green.

Define those first in terms of some frequency band and the job is done.

OpticsEngineer said:

Interesting graphic

six colors of dinosaurs. but seven colors in the rainbow.

Click to expand...

Yes, my take is the artist missed out Indigo, and Violet was called Purple.

(Or perhaps it was just after the great extinction, and the Indigo Dinosaurs were the first to go.)

Ephemeris said:

Ruud uit de Graaf said:

Tom Axford said:

This test seems to have been doing the rounds recently.

Click to expand...

Thanks! This can solve a dispute with my wife about what is green, what is blue...
I was not in the midle ;-)

Ruud

Click to expand...

Surely this makes little sense.

It is using some words, namely blue and green.

Define those first in terms of some frequency band and the job is done.

Click to expand...

As a former engineer I do agree to your approach, my wife doesn't ;-o

Ruud uit de Graaf said:

Ephemeris said:

Ruud uit de Graaf said:

Tom Axford said:

This test seems to have been doing the rounds recently.

Click to expand...

Thanks! This can solve a dispute with my wife about what is green, what is blue...
I was not in the midle ;-)

Ruud

Click to expand...

Surely this makes little sense.

It is using some words, namely blue and green.

Define those first in terms of some frequency band and the job is done.

Click to expand...

As a former engineer I do agree to your approach, my wife doesn't ;-o

Click to expand...

In that case I think we both lost the argument

DaveR43 said:

OpticsEngineer said:

Interesting graphic

six colors of dinosaurs. but seven colors in the rainbow.

Click to expand...

Yes, my take is the artist missed out Indigo, and Violet was called Purple.

(Or perhaps it was just after the great extinction, and the Indigo Dinosaurs were the first to go.)

Click to expand...

See also this post about the colour Purple... Which isn't a colour in the rainbow...

OpticsEngineer said:

All my old optical textbooks break up the rainbow into six colors bands. (Red, Orange, Yellow, Green, Blue, Violet)

The familiar picture of a prism on the Pink Floyd's The Dark Side of the Moon also depicts six color bands (from 1973).

However, I see on Wikipedia the assignment of seven color bands. (Red, Orange, Yellow, Green, Cyan, Blue, Violet)

Visible spectrum - Wikipedia

I am looking at my Dark Side of the Moon album cover and the color between green and violet looks blue (and a very lovely blue too I might add), whereas when I pull up an image on it on my computer monitor, what I see in between green and violet looks like cyan.

Is the assignment of seven color bands in the spectrum becoming an accepted system? Maybe driven by the increasing use of electronic displays?

I have been using blue and cyan optical filters for my entire career, and navigating the worlds of additive and subtractive colors with clarity of communication with other professionals. But is there shift going on in terminology that I need to keep up with?

(edit: within five minutes of posting this I got three advertisements on my web browser for cyan house paints. make of that what you will)

Click to expand...

Blame Isaac Newton! He started with 5 colour bands, shifted to 7 and also considered 10 (although he conceded that the real number was probably infinite). The 5 and 7 sequence arise primarily from his interest in music and the pentatonic and heptatonic (diatonic/Aeolian/Dorian) scales, white notes on a piano but not in equal temperament. He also believed that the sensation of colour was transmitted from the eye to the brain via transverse vibration of the optic nerve, another musical analogy.

Newton's Green is not the same as seen in other colour representations; the orange plus indigo were inserted to match musical scales, rather than based on other fundamentals (he rejected 6 bands). Newton also viewed Yellow as a primary and many still do because of its perceptual, rather than physical properties: It is perceptually the brightest colour, one of the 4 unique hues and has also has the greatest colour contrast, when placed on a black background. The opponent colour model reinforces this view, although developed considerably later. There is also the NCS Swedish Colour Model, still in use today but I'm not sure of its influence outside of Scandinavia.



Newton also discovered (don't try this at home) that complementary colour could be generated by compressing his own eyeball, using a bodkin placed between his eye and the inside of his skull then applying some leverage! https://www.laphamsquarterly.org/discovery/true-colors

Objectively, there are no bands as it's a continuous spectrum from IR to UV including all single wavelength colours. Subjectively there may be bands, and they are and are namec whatever you personally decide. If you're in a group, why not vote on it?

Thanks for the link to the good review of historical color concepts.

I found this section particularly well pointed to my question:

"Partly because the traditional "artists' colour wheel" has a place for orange but only one blue, the spotlight of skepticism has mostly fallen on Newton's indigo, although some relief has arrived in recent decades in the form of the RGB(CMY) hue circle, which recognizes a deep "blue" and cyan as separate hues. The modern meaning for "cyan" of greenish blue dates from Helmholtz (1866)"

OpticsEngineer said:

Thanks for the link to the good review of historical color concepts.

I found this section particularly well pointed to my question:

"Partly because the traditional "artists' colour wheel" has a place for orange but only one blue, the spotlight of skepticism has mostly fallen on Newton's indigo, although some relief has arrived in recent decades in the form of the RGB(CMY) hue circle, which recognizes a deep "blue" and cyan as separate hues. The modern meaning for "cyan" of greenish blue dates from Helmholtz (1866)"

Click to expand...

Thanks for pointing this out; when I did the test mentioned in Tom Axford's posting very early in the thread (This test seems to have been doing the rounds recently.), I felt that much of the time I was looking at Cyan, not Blue or Green...

This may help:

DaveR43 said:

OpticsEngineer said:

Thanks for the link to the good review of historical color concepts.

I found this section particularly well pointed to my question:

"Partly because the traditional "artists' colour wheel" has a place for orange but only one blue, the spotlight of skepticism has mostly fallen on Newton's indigo, although some relief has arrived in recent decades in the form of the RGB(CMY) hue circle, which recognizes a deep "blue" and cyan as separate hues. The modern meaning for "cyan" of greenish blue dates from Helmholtz (1866)"

Click to expand...

Thanks for pointing this out; when I did the test mentioned in Tom Axford's posting very early in the thread (This test seems to have been doing the rounds recently.), I felt that much of the time I was looking at Cyan, not Blue or Green...

Click to expand...

I agree with you.