Colours in the rainbow, etc

[excreationist]

When I was in hospital a few weeks ago I thought about colours...


there are additive colours (light) - (RGB)
red, green and blue. When combined in pairs they make yellow, cyan and magenta. All together they make white.


the subtractive colours (pigment) -(CMY/CMYK [blacK])
cyan, magenta, yellow - in pairs they make blue, red, green. All together make black.


There was a poster in the hospital that said the primary colours are red, blue and yellow. But when those paints are combined I think they make brown, not black - so they can't be used to make any colour. I'd tell staff that it was wrong. I think it is just a tradition that they involve red, blue and yellow.


People normally say there is purple in the rainbow - but violet is actually blue. ("violets are blue")


Rainbows go from red to blue:
http://www.giangrandi.ch/optics/spectrum/visible-a.png


I heard that rainbows can have purple in them when there is a double rainbow (blue plus red)


In some ways there are only 3 colours in the rainbow:


red, green and blue - yellow and orange come from red and green and there is cyan (green plus blue)


In some ways there are 7 colours:


infra-red, red, yellow, green, cyan, blue, ultra-violet

 

[excreationist]

https://en.wikipedia.org/wiki/Rainbow#Number_of_colours_in_spectrum_or_rainbow
"...Scholars have noted that what Newton regarded at the time as "blue" would today be regarded as cyan, and what Newton called "indigo" would today be considered blue..."

 

[bigfield]

Most humans have trichromatic vision. We have sensors for three colours: red, green and blue. All of the colours we see are combinations of sensory input corresponding to those three colours. Depending on the quality of one's colour vision, a person can differentiate up to millions of different colours.

Some people are deficient in one of more of those colours, and some women can see a fourth colour, but our social construction of colour doesn't extend to tetrachromatic vision.

So the rainbow has either three colours or millions of colours, but not seven.

Do infrared and ultraviolet count as colours, if no-one can see them, or are they just names for wavelengths outside our visual spectrum?

 

[excreationist]

Most humans have trichromatic vision. We have sensors for three colours: red, green and blue. All of the colours we see are combinations of sensory input corresponding to those three colours. Depending on the quality of one's colour vision, a person can differentiate up to millions of different colours.

Some people are deficient in one of more of those colours, and some women can see a fourth colour, but our social construction of colour doesn't extend to tetrachromatic vision.

So the rainbow has either three colours or millions of colours, but not seven.

I'm talking about named colours... if you are talking about millions of colours it isn't clear which ones are distinct for different people.

Do infrared and ultraviolet count as colours, if no-one can see them, or are they just names for wavelengths outside our visual spectrum?

Some animals can...
https://cosmosmagazine.com/biology/incredible-bizarre-spectrum-animal-colour-vision
"...Some birds see colour and ultraviolet..."
"...Boas and pythons can 'see' in the infrared..."
".....The bluebottle butterfly has 15 types of photoreceptor..."

More stuff about animal colour vision:
https://en.wikipedia.org/wiki/Color_vision

https://en.wikipedia.org/wiki/Infrared_vision
"...researchers developed a neural implant that gives rats the ability to sense infrared light..."

People can see it using technology - including using phones to see the infrared light from a remote:
https://www.youtube.com/watch?v=O0dbxf_ToJU&t=50

I think in the future humans vision would be enhanced to see UV and infrared....

 

[Valjean]

Color terms are usually colloquial; they vary, as do an individuals perception of them. If you want to be specific you have to use some formal designation, like its Hex number.
There are various technical color schemes. Artists', physicists' and photographic schema differ.

Purple/violet?
IMHO: Add a little red to blue and you get violet, add some more and you get purple, still more and you have magenta.

Fuschia? -- anyone's guess.

 

[bigfield]

Most humans have trichromatic vision. We have sensors for three colours: red, green and blue. All of the colours we see are combinations of sensory input corresponding to those three colours. Depending on the quality of one's colour vision, a person can differentiate up to millions of different colours.

Some people are deficient in one of more of those colours, and some women can see a fourth colour, but our social construction of colour doesn't extend to tetrachromatic vision.

So the rainbow has either three colours or millions of colours, but not seven.

I'm talking about named colours... if you are talking about millions of colours it isn't clear which ones are distinct for different people.

Well, in that case, there's far more than seven named colours.

There are plenty of examples in this list: https://www.colorhexa.com/color-names

Do infrared and ultraviolet count as colours, if no-one can see them, or are they just names for wavelengths outside our visual spectrum?

Some animals can...
https://cosmosmagazine.com/biology/incredible-bizarre-spectrum-animal-colour-vision
"...Some birds see colour and ultraviolet..."
"...Boas and pythons can 'see' in the infrared..."
".....The bluebottle butterfly has 15 types of photoreceptor..."

More stuff about animal colour vision:
https://en.wikipedia.org/wiki/Color_vision

https://en.wikipedia.org/wiki/Infrared_vision
"...researchers developed a neural implant that gives rats the ability to sense infrared light..."

None of which can name colours, though.

People can see it using technology - including using phones to see the infrared light from a remote:
https://www.youtube.com/watch?v=O0dbxf_ToJU&t=50

I think in the future humans vision would be enhanced to see UV and infrared....

But we don't see it as a colour; our devices see it and then display a wavelength of light we can see. Same goes for night-vision and thermal optics technology, or fluorescence.

 

[bigfield]

there are additive colours (light) - (RGB)
red, green and blue. When combined in pairs they make yellow, cyan and magenta. All together they make white.


the subtractive colours (pigment) -(CMY/CMYK [blacK])
cyan, magenta, yellow - in pairs they make blue, red, green. All together make black.

Interestingly the cyan used in print is actually very different than that used in computer graphics. Cyan in the HTML palette is a simple combination of blue and green, but cyan in a four-colour process is basically blue.

 

[Jimmy Higgins]

While there are transitional colors, the rainbow, which is viewed from quite a distance does seem to have a finite number of distinct colors.

 

[excreationist]

Color terms are usually colloquial; they vary, as do an individuals perception of them. If you want to be specific you have to use some formal designation, like its Hex number....

Ok:
red: #f00
green: #0f0
blue: #00f
cyan: #0ff
magenta: #f0f
yellow: #ff0

 

[excreationist]

....There are plenty of examples in this list: https://www.colorhexa.com/color-names

Colours like "dark blue" don't technically have a standard hex value.

None of which can name colours, though.

This parrot can count items according to color so I think it would be able to name colors.
https://www.youtube.com/watch?v=7yGOgs_UlEc

...But we don't see it as a colour; our devices see it and then display a wavelength of light we can see. Same goes for night-vision and thermal optics technology, or fluorescence.

Phones see infrared light as additional brightness I think.

 

[excreationist]

.....Interestingly the cyan used in print is actually very different than that used in computer graphics. Cyan in the HTML palette is a simple combination of blue and green, but cyan in a four-colour process is basically blue.

Hmmm... on wikipedia quite a bit the cyan looked too dark.... I thought it was wrong!

I thought on some inkjet printers they use bright cyan:
http://caionascimento.me/wp-content...stomer-support-for-hp-color-test-page-pdf.jpg

I thought if the cyan wasn't bright enough then just using half toning would make it less saturated (because it is adding white)

 

[bigfield]

Colours like "dark blue" don't technically have a standard hex value.

Yes it does: #00008B.

color:darkblue is a valid CSS rule. How much more standard do we need to get?

This parrot can count items according to color so I think it would be able to name colors.
https://www.youtube.com/watch?v=7yGOgs_UlEc

It doesn't, though.

...But we don't see it as a colour; our devices see it and then display a wavelength of light we can see. Same goes for night-vision and thermal optics technology, or fluorescence.

Phones see infrared light as additional brightness I think.

That makes sense; any light that a camera's sensor picks up counts towards brightness. However, the picture you see on the phone screen shows it as white light, which is a mixture of wavelengths in the human visible spectrum.

My point is that unless our eyes are sensing the infrared light directly, we aren't seeing it.

 

[excreationist]

Yes it does: #00008B.

color:darkblue is a valid CSS rule. How much more standard do we need to get?

Ok you've got a point

 

[excreationist]

This parrot can count items according to color so I think it would be able to name colors.
https://www.youtube.com/watch?v=7yGOgs_UlEc

It doesn't, though.

https://en.wikipedia.org/wiki/Alex_(parrot)

For example, when Alex was shown an object and was asked about its shape, color, or material, he could label it correctly.

It can label colors correctly...

.....Looking at a mirror, he said "what color", and learned "grey" after being told "grey" six times. This made him the first and only non-human animal to have ever asked a question (apes who have been trained to use sign-language have so far failed to ever ask a single question).

that's impressive...

 

[bigfield]

https://en.wikipedia.org/wiki/Alex_(parrot)

For example, when Alex was shown an object and was asked about its shape, color, or material, he could label it correctly.

It can label colors correctly...

.....Looking at a mirror, he said "what color", and learned "grey" after being told "grey" six times. This made him the first and only non-human animal to have ever asked a question (apes who have been trained to use sign-language have so far failed to ever ask a single question).

that's impressive...

What I meant is: can Alex the parrot, or any animal for that matter, name a colour humans can't see?

If not then animals can't contribute to the social construction that is named colours.

 

[excreationist]

What I meant is: can Alex the parrot, or any animal for that matter, name a colour humans can't see?

If not then animals can't contribute to the social construction that is named colours.

Well they can recognise UV that is reflected on things
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691211/
So I think it would be possible for a parrot to name it. BTW it took me quite a while to find an example of Alex naming colors even though it seemed pretty obvious that it could (since it could count objects of a specified color)