Technology1 min ago
The primary colours
14 Answers
We've all been told from an early age that mixing blue and yellow gives you green, and have proved this correct by doing it.
The primary colours red, blue and yellow, are the 3 colours from which all others are made.
So why do we often hear these days that the 3 primary colours are red, green and yellow?
You can not make purple from any combination of this trio, can you?
The primary colours red, blue and yellow, are the 3 colours from which all others are made.
So why do we often hear these days that the 3 primary colours are red, green and yellow?
You can not make purple from any combination of this trio, can you?
Answers
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You are maybe thinking of Red, Green and Blue. They are the primary colours of light (as in a TV set).
Colours of light work in a subtractive way rather than the expected additive way of paint. Mix blue and yellow paint and yes you get green. However, if you shine a green and a blue light at the same spot, it will look yellow.
I've not heard of red, green and yellow being any form of promary colour.
Colours of light work in a subtractive way rather than the expected additive way of paint. Mix blue and yellow paint and yes you get green. However, if you shine a green and a blue light at the same spot, it will look yellow.
I've not heard of red, green and yellow being any form of promary colour.
I think squarebear has got slightly muddled.
Light mixes my the ADDITIVE process
Pigments mix by the SUBTRACTIVE process
When dealing with pigments, artists always say the primary colours are red, yellow and blue but more scientifically, these should be magenta, yellow and cyan which are the three pigments used in the printing industry (along with black) to reproduce all the colours you see in colour magazines. You will also see those colours in in ink cartridges of ink-jet printers and the toners in colour laser printers.
Light mixes my the ADDITIVE process
Pigments mix by the SUBTRACTIVE process
When dealing with pigments, artists always say the primary colours are red, yellow and blue but more scientifically, these should be magenta, yellow and cyan which are the three pigments used in the printing industry (along with black) to reproduce all the colours you see in colour magazines. You will also see those colours in in ink cartridges of ink-jet printers and the toners in colour laser printers.
gen 2 has it perfectly correct. I don't know why teachers and parents have told children for yonks that the primary colours are red, blue and yellow (which are actually two primaries and a secondary).
To get any colour visible to humans from a three-colour paint-box those colours (as gen2 says) would have to be magenta, cyan and yellow. Did adults think that the words "magenta" and "cyan" were too difficult for children? More difficult than "yellow" or "purple"?
It is even more mysterious in this modern age when everyone can see (if he looks closely enough) that his colour television picture is made up (additively) of pixels coloured red, green, and blue - the primaries - and that his computer's printer inks (and the dots in the centre-fold of his newspaper) are magenta, cyan and yellow - the secondaries, or complementaries.
It seems that childhood indoctrination is more powerful than everday observation.
To get any colour visible to humans from a three-colour paint-box those colours (as gen2 says) would have to be magenta, cyan and yellow. Did adults think that the words "magenta" and "cyan" were too difficult for children? More difficult than "yellow" or "purple"?
It is even more mysterious in this modern age when everyone can see (if he looks closely enough) that his colour television picture is made up (additively) of pixels coloured red, green, and blue - the primaries - and that his computer's printer inks (and the dots in the centre-fold of his newspaper) are magenta, cyan and yellow - the secondaries, or complementaries.
It seems that childhood indoctrination is more powerful than everday observation.
Contrary to popular belief there are no absolute primary colours. A primary triad is a combination of colours where the third cannot be made from the other two.
As stated by others this process depends on whether the colours are light sources (additive) or absorbers (subtractive). In practice Red, Green and Blue are used for additives while Magenta, Cyan and Yellow are used for subtractives.
A set of primary subtractives has a corresponding set of complementary primary additives. Don't get confused. Remember colours on the right are additive. Mixing these paints won't make the subtractive colour on the left.
Magenta = (not green) or (Red + blue);
Cyan = (not Red) or (Green + Blue) ;
Yellow = (not Blue) or (Red + Green)
The confusion about RGB or RGY being the primary colours for paints is because neither combination is correct. No matter what proportions you use you will never get white by mixing these combinations.
Try this. Get coloured pencils in Mg, Cy and Y. Gently colour a small area of white paper with some of each. Now rub it together with a piece of blotting paper and presto it actually disappears back to white.
Do this with RGB or RGY and you will never get anything except a colour or shade of grey.
As stated by others this process depends on whether the colours are light sources (additive) or absorbers (subtractive). In practice Red, Green and Blue are used for additives while Magenta, Cyan and Yellow are used for subtractives.
A set of primary subtractives has a corresponding set of complementary primary additives. Don't get confused. Remember colours on the right are additive. Mixing these paints won't make the subtractive colour on the left.
Magenta = (not green) or (Red + blue);
Cyan = (not Red) or (Green + Blue) ;
Yellow = (not Blue) or (Red + Green)
The confusion about RGB or RGY being the primary colours for paints is because neither combination is correct. No matter what proportions you use you will never get white by mixing these combinations.
Try this. Get coloured pencils in Mg, Cy and Y. Gently colour a small area of white paper with some of each. Now rub it together with a piece of blotting paper and presto it actually disappears back to white.
Do this with RGB or RGY and you will never get anything except a colour or shade of grey.
beso, you are confusing the issue. The primary colours are not to do with mixing pigments but with mixing light, where:
R + G + B = White
You can check this by looking closely at a white patch on a colour CRT TV screen, where you will see the red, green and blue patches glowing equally brightly. Any other colour visible to the human eye can be made by mixing R, G and B lights in various proportions.
To get any colour from pigments you use various proportions of the complements of R, G, and B (that is, white light minus that colour) which are respectively Cyan, Magenta and Yellow.
These three mixed together equally will, all too logically, give black.
For some reason grown-ups reckoned that children would not understand magenta and cyan and so approximated them to red and blue respectively, falsely claiming that it is R, B and Y that can produce any colour.
Colour printer cartridges and newspaper centre-fold dots are gradually re-educating people.
R + G + B = White
You can check this by looking closely at a white patch on a colour CRT TV screen, where you will see the red, green and blue patches glowing equally brightly. Any other colour visible to the human eye can be made by mixing R, G and B lights in various proportions.
To get any colour from pigments you use various proportions of the complements of R, G, and B (that is, white light minus that colour) which are respectively Cyan, Magenta and Yellow.
These three mixed together equally will, all too logically, give black.
For some reason grown-ups reckoned that children would not understand magenta and cyan and so approximated them to red and blue respectively, falsely claiming that it is R, B and Y that can produce any colour.
Colour printer cartridges and newspaper centre-fold dots are gradually re-educating people.
Point taken chakka about the concept of subtractive primaries. It is a matter of definition I guess but the concept is valid.
Like I said.
Magenta is white minus green etc.
Note however that it is the relative content of colours that determines the hue. Paints work by removing some of the reflected light. of particular colours. Some green light is still reflected from magenta (etc) because pigments are not totally absorbtive.
Superficial logic might suggest mixing Magenta, Cyan and Yellow will make black but it doesn't. What it does is make a white area that is less reflective than the original paper.
Certainly if you did manage to get total absorbtion it would be black.
Like I said.
Magenta is white minus green etc.
Note however that it is the relative content of colours that determines the hue. Paints work by removing some of the reflected light. of particular colours. Some green light is still reflected from magenta (etc) because pigments are not totally absorbtive.
Superficial logic might suggest mixing Magenta, Cyan and Yellow will make black but it doesn't. What it does is make a white area that is less reflective than the original paper.
Certainly if you did manage to get total absorbtion it would be black.
-- answer removed --
For an alternative approach to answering the question of what are the primary colours perhaps we should first answer the question of what makes a colour �primary�.
While adding light of specific wavelengths centered around red blue and green do approximate the perception of other colours such as yellow orange cyan megenta these perceptions are an illusion brought about by virtue of the process our eyes use to discriminate colours. Colour discrimination is achieved visually by comparing intensities of three bands of colour centered around the frequencies of red blue and green to which three different types of cones in the retina of the eye are most sensitive. Mixing various colours of light does not produce a new intermediate wavelength. The eye 'sees' the true wavelength of, for instance, "yellow" by the affect that wavelength of light has of stimulating in certain ratios the red, blue and green receptors of the retina.
The ability to stimulate the full gamit of colours that the eye can distinguish is best accomplished by choosing the three wavelengths of light that produce the most discrete stimulation to each of the three types of cones in the eye. Although the three most suitable colours for this purpose vary slightly between individuals, testing a large sample of people with �normal� visual responses allows us to choose the three specific wavelengths of light which produce the greatest possible gamit of colour variation and range among the largest range of viewers. These colours of red, green, and blue would then be defined by the specific wavelength of each.
In practice a certain amount of compromise is taken in selecting the actual colours used due to availability and efficiency in producing the ideal wavelengths.
more here
While adding light of specific wavelengths centered around red blue and green do approximate the perception of other colours such as yellow orange cyan megenta these perceptions are an illusion brought about by virtue of the process our eyes use to discriminate colours. Colour discrimination is achieved visually by comparing intensities of three bands of colour centered around the frequencies of red blue and green to which three different types of cones in the retina of the eye are most sensitive. Mixing various colours of light does not produce a new intermediate wavelength. The eye 'sees' the true wavelength of, for instance, "yellow" by the affect that wavelength of light has of stimulating in certain ratios the red, blue and green receptors of the retina.
The ability to stimulate the full gamit of colours that the eye can distinguish is best accomplished by choosing the three wavelengths of light that produce the most discrete stimulation to each of the three types of cones in the eye. Although the three most suitable colours for this purpose vary slightly between individuals, testing a large sample of people with �normal� visual responses allows us to choose the three specific wavelengths of light which produce the greatest possible gamit of colour variation and range among the largest range of viewers. These colours of red, green, and blue would then be defined by the specific wavelength of each.
In practice a certain amount of compromise is taken in selecting the actual colours used due to availability and efficiency in producing the ideal wavelengths.
more here
Nothing to argue wit there, Mib.
Beso, the reason that you get black when you mix the three pigments known as complementary, secondary or "artist's primaries" is that cyan absorbs the red, magenta the green and yellow the blue from white light, giving black.
I seem to remember that there's a choice (someone remind me) in computer printing whether you have a black from the black cartridge or a mixed black from the three colour cartridges.
Beso, the reason that you get black when you mix the three pigments known as complementary, secondary or "artist's primaries" is that cyan absorbs the red, magenta the green and yellow the blue from white light, giving black.
I seem to remember that there's a choice (someone remind me) in computer printing whether you have a black from the black cartridge or a mixed black from the three colour cartridges.
Wow! Hi everybody! I never imagined that my question would cause so much controversy, or draw such complex technical answers, with everybody having slightly different shades (...ha!) of opinion as to what's correct.
To the first answer - yes, I think I was probably thinking of Red, Green and Blue, now you mention it.
I was not aware of this difference between additive and subtractive colours, and I can't say I particularly understand the fine detail of the science behind this, or the distinction between the two. There is clearly something odd going on between what you get from paint and what you get from light. I still have difficulty seeing Green as a primary colour, when I know that it can be made from mixing Blue and Yellow. So what do you get if you mix Blue and Yellow light? And what light would you mix from Red, Green and Blue to get Purple, or Orange? I'll bet the answers to those questions are going to cause somersaults in my head!
Thanks to all for the very detailed responses.
To the first answer - yes, I think I was probably thinking of Red, Green and Blue, now you mention it.
I was not aware of this difference between additive and subtractive colours, and I can't say I particularly understand the fine detail of the science behind this, or the distinction between the two. There is clearly something odd going on between what you get from paint and what you get from light. I still have difficulty seeing Green as a primary colour, when I know that it can be made from mixing Blue and Yellow. So what do you get if you mix Blue and Yellow light? And what light would you mix from Red, Green and Blue to get Purple, or Orange? I'll bet the answers to those questions are going to cause somersaults in my head!
Thanks to all for the very detailed responses.
Combining red and green light produce the secondary color we perceive as yellow. Adding blue light on top of that combination produces the perception we identify as white (even more so if the background the light is shining on is white to begin with)!
looky here
looky here
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