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Geoff Ingram wrote:

Colours don't really exist anyway. They are generated in our brains, which assign this representation in our minds depending on what sensors in our retina are stimulated. 

So did that dress not even have colours?

https://xkcd.com/1492/

Outside our heads, no. The picture reflects some light waves, absorbs others and those that reach our eyes make us "see" colours. Since everybody's cone cells are slightly, and sometimes very, different, as in daltonism, a range of possible colour interpretations are valid. Birds have 4 different types of photoreceptors and thus see vastly more colours. As do a very reduced number of humans.

Pretty sure I read about this last Monday in the Grauniad, but I can't find the article now. Sorry.

Geoff Ingram wrote:

Outside our heads, no. The picture reflects some light waves, absorbs others and those that reach our eyes make us "see" colours. Since everybody's cone cells are slightly, and sometimes very, different, as in daltonism, a range of possible colour interpretations are valid. Birds have 4 different types of photoreceptors and thus see vastly more colours. As do a very reduced number of humans.

Pffft! Mantis shrimps laugh at your tetrachromacy

https://theoatmeal.com/comics/mantis_shrimp

I hate it when someone reminds me about xkcd.  I lose hours of time...

Anyhoo - found this one at https://xkcd.com/2766/

peted76 wrote:

.

Steve K wrote:

OK - my "thinking too hard about things that don't matter" rant.  Why is pink a separate colour anyway?  Add white to blue, you get light blue.  Add white to green, you get light green.  Same with every colour except red.  Pink should just be 'light red'.

Don't worry about it. An often-used shade of pink doesn't even exist.

https://medium.com/swlh/magenta-the-color-that-doesnt-exist-and-why-ec40...

ShutTheFrontDawes wrote:

Steve K wrote:

OK - my "thinking too hard about things that don't matter" rant.  Why is pink a separate colour anyway?  Add white to blue, you get light blue.  Add white to green, you get light green.  Same with every colour except red.  Pink should just be 'light red'.

Don't worry about it. An often-used shade of pink doesn't even exist. https://medium.com/swlh/magenta-the-color-that-doesnt-exist-and-why-ec40...

Hold on a minute - does that mean that gays have stolen the colour "pink"? They've already got the whole rainbow, how many more colours do they want?

hawkinspeter wrote:

ShutTheFrontDawes wrote:

Steve K wrote:

OK - my "thinking too hard about things that don't matter" rant.  Why is pink a separate colour anyway?  Add white to blue, you get light blue.  Add white to green, you get light green.  Same with every colour except red.  Pink should just be 'light red'.

Don't worry about it. An often-used shade of pink doesn't even exist. https://medium.com/swlh/magenta-the-color-that-doesnt-exist-and-why-ec40...

Hold on a minute - does that mean that gays have stolen the colour "pink"? They've already got the whole rainbow, how many more colours do they want?

How can they steal something that doesn't even exist? Or maybe it used to be in the rainbow but it isn't anymore because they've half-inched it... I'm going for a lie down.

Perhaps that colour exists, but is only visible to certain gaze?

hawkinspeter wrote:

ShutTheFrontDawes wrote:

Steve K wrote:

OK - my "thinking too hard about things that don't matter" rant.  Why is pink a separate colour anyway?  Add white to blue, you get light blue.  Add white to green, you get light green.  Same with every colour except red.  Pink should just be 'light red'.

Don't worry about it. An often-used shade of pink doesn't even exist. https://medium.com/swlh/magenta-the-color-that-doesnt-exist-and-why-ec40...

Hold on a minute - does that mean that gays have stolen the colour "pink"? They've already got the whole rainbow, how many more colours do they want?

The internet is yours for the day!

Far from stopping me worrying about it, you're just making me worry about that, too.

Steve K wrote:

OK - my "thinking too hard about things that don't matter" rant.  Why is pink a separate colour anyway?  Add white to blue, you get light blue.  Add white to green, you get light green.  Same with every colour except red.  Pink should just be 'light red'.

Dredging up physics lessons from 40 years ago, I can remember being told that pink is not light red, pink is in fact a combination of red and purple from different parts of the spectrum in the same way that brown is a combination of red, blue and yellow, and that gave it the "right" to have its own individual name. If this is wrong, feel free to take it up with Mr Wallace. Though thinking about it if he's still alive he would be well into three figures so…

Does this help?

Sigh... at least this rabbithole is colourful though...

https://en.m.wikipedia.org/wiki/CIE_1931_color_space

https://en.m.wikipedia.org/wiki/Impossible_color

I don't know where to start here.

Colour is a sensation that only exists within the brain. (Do you see colours when you dream?)
There are an infinite number of colours, but the human eye can detect about 10 million (depending on which textbook you read). The English language has eleven true colour names, pink is one of them. Other languages may have a different number.
The colour we "see" depends on three things, the fundamental colour of the object (reflectance), the ambient light (Illuminant), and the human eye/brain combination.
The diagram above is of an undefined colour space (Check out CIELab for a definitive one) Color space is three dimensional, imagine it is sherical like the Earth. In this diagram we are looking down on the North Pole,  white and pastel colours near the centre and all the brightest colours around the Equator. If we took a section through the Equator we would have a neutral grey in the centre with more subdued colours surrounding it.

Sorry to be a bore, but it used to be my job

Cycloid wrote:

There are an infinite number of colours, but the human eye can detect about 10 million (depending on which textbook you read).

I'd like to be able to see more colours, please. Which textbook do I have to read to make it happen?

I would recommend the Terry Pratchet Discworld novels. The Newtonian Spectrum contains Seven colours. On Discworld we have an eighth color - Octarine which expands the visual spectrum.
The sooner you fuck off there the better.

Cycloid wrote:

I would recommend the Terry Pratchet Discworld novels. The Newtonian Spectrum contains Seven colours. On Discworld we have an eighth color - Octarine which expands the visual spectrum.
The sooner you fuck off there the better.

That's not even a textbook, it's just a book with text in it.

Cycloid wrote:

I would recommend the Terry Pratchet Discworld novels. The Newtonian Spectrum contains Seven colours. On Discworld we have an eighth color - Octarine which expands the visual spectrum.
The sooner you fuck off there the better.

Newton's decision to define the spectrum as seven colours was pretty arbitary - it was actually to align it to a musical octave (which, despite the name, is seven notes).

You are 100% correct, Newton could have used any selection of colours from the spectrum. Most people don't see indigo. the crazy thing is that we still teach Newton's spectrum in schools 350 odd years later.

Cycloid wrote:

You are 100% correct, Newton could have used any selection of colours from the spectrum. Most people don't see indigo. the crazy thing is that we still teach Newton's spectrum in schools 350 odd years later.

I thought it was because a Richard of York had recently given battle in vain.

Take a can of brilliant white emulsion, put a spot of red in it, you get pink. Pink is a very light red.

Take a bright orange, put some black in it you will get brown. Brown is a dirty orange.

Generally speaking you can match any colour paint with the correct combination of yellow, red, blue pigments.

Cycloid wrote:

Take a can of brilliant white emulsion, put a spot of red in it, you get pink. Pink is a very light red.

Take a bright orange, put some black in it you will get brown. Brown is a dirty orange.

Generally speaking you can match any colour paint with the correct combination of yellow, red, blue pigments.

Also, take a load of white t-shirts and put them in a wash with one red sock...

Why didn't I think of that?

Cycloid wrote:

Take a can of brilliant white emulsion, put a spot of red in it, you get pink. Pink is a very light red.

But why do you see pink? Because your paint is reflecting to you the red and purple portions of the spectrum, not because it's reflecting back a little bit of red and a lot of white light.