I came across this paragraph in this website:

Any three colors (or frequencies) of light that produce white light when combined with the correct intensity are called primary colors of light. There are a variety of sets of primary colors. The most common set of primary colors is red (R), green (G) and blue (B).

It says, there are a variety sets of primary colors. Can you name other primary colors of light other than RGB based on the above definition?

Based on this definition C, M and Y in CMY color model or R, Y and B in RYB color model are not primary colors. This is in contrast to the defintion in Wikipedia.

closed as off-topic by Philip Kendall, Tetsujin, scottbb, Itai, mattdm Feb 20 '18 at 1:14

  • This question does not appear to be about photography within the scope defined in the help center.
If this question can be reworded to fit the rules in the help center, please edit the question.

  • 3
    I'm voting to close this question as off-topic because it doesn't seem to have anything to do with photography. – Philip Kendall Feb 19 '18 at 11:12
  • Can you please point me to the right stack exchange forum? – ManiAm Feb 19 '18 at 11:17
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    @PhilipKendall if the question was a bit edited to be about CMYK, RGB and if there are other systems - or why RGB is chosen - then I'd think it would make perfect sense here. – flolilo Feb 19 '18 at 11:19
  • This website has good articles on the subject. – Aram Hăvărneanu Feb 19 '18 at 12:40
  • Maybe physics.stackexchange.com? – mattdm Feb 20 '18 at 1:14

Light spectrum vs. color sets

Your citation misses the most important parts of the paragraph. In my opinion, this is the important part:

[...] When we speak of white light, we are referring to ROYGBIV [Link to Wikipedia's article on ROYGBIV] - the presence of the entire spectrum of visible light. But combining the range of frequencies in the visible light spectrum is not the only means of producing white light. White light can also be produced by combining only three distinct frequencies of light, provided that they are widely separated on the visible light spectrum. Any three colors (or frequencies) of light that produce white light when combined with the correct intensity are called primary colors of light. [...]

As Wikipedia states in its simple article about primary colors:

Primary colors [...] are sets of colors that can be combined to make a useful range of colors. The primary colors are those which cannot be created by mixing other colors in a given color space.

For subtractive combination of colors, as in mixing of pigments or dyes for printing, the primaries normally used are cyan, magenta, and yellow, though the set of red, yellow, blue is popular among artists.

For additive combination of colors, as in overlapping projected lights or in CRT displays, the primary colors normally used are red, green, and blue.

In your case, we are talking about additive color models.

Additive and subtractive color models

Additive, as in "all primary colors together are white by adding them". Red cannot be mixed by adding blue to green, blue cannot be mixed by adding green to red, and green cannot be mixed by adding blue to red:

additive color mixing by Wikipedia

Stolen from Wikipedia

Subtractive, as in "all primary colors together are black by subtracting them". Cyan cannot be mixed by subtracting magenta from yellow, yellow cannot be mixed by subtracting magenta from cyan, and magenta cannot be mixed by subtracting cyan from yellow:

Subtractive color mixing by Wikipedia

Stolen from Wikipedia

Creating your own primary color set

color wheel

Stolen from the Internet

Therefore, it is a simple matter of making up your own system of colors that fall within the specification of primary colors. Take the above color-wheel and take any equidistant positioned set of 2-3 colors1, preferably from the outer lane - and voilà, you have a set of primary colors.

1 Even 4+ colors could work. There will be a limit where primary colors suddenly will lose their uniqueness, as the one in the middle between two can get mixed by its negative and its positive neighbours. Depending on accuracy, this could be somewhere between 90° to 0,000001°. To help you visualize it, just imagine a straight line between point A and point C and see how close it comes to point B.

Furthermore, you can try Adobe's interactive color wheel to find different combinations.

  • This is not the answer to my question! And I checked wikipedia before posting too! – ManiAm Feb 19 '18 at 11:26
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    it absolutely is. parsing hexadecimal color codes isn't really what photo.SE is about. however, I added a paragraph so it becomes more clear. – flolilo Feb 19 '18 at 11:36
  • I appreciate your answer, but I guess you did not read my question carefully. Primary colors, based on the definition in the physics website that I provided, are defined as set of three colors that produce white when combined. C,M,Y in CMY model are not primary colors. R, Y, B are not primary colors in RYB based on this definition. – ManiAm Feb 19 '18 at 11:43
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    RYB would be oprimary, as you cannot get yellow out of blue and red. mind you, you could not get to white, either. besides that: do you just want to discuss? SE is for asking serious questions, not for philosophical-style "define "color" for me - and then, let us talk about your definition!" – flolilo Feb 19 '18 at 11:59
  • please explain what you mean by "diametral positioned" and how you get 3 colours that way. – ths Feb 19 '18 at 12:32

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