I went through an article on color connotations and it did not explain why colors are grouped as primary and secondary so I don't know if it is important to know the reason why we have:

warm color red -> orange -> yellow (red and yellow being primary colors)

cold colors green -> blue -> purple (blue being primary color)

My questions: a) Is there an important reason why these are the primary colors? b) Is their a rule on how these groups (primary and secondary) colors should be used. for example would you ever say "for this element you need a primary color) c) Would you use cold and warm colors together in a website d) how important is to know how (for example) information like blue + yellow = green

Also (might seem slightly of topic) I started experimenting with the color while and I don't get where would you chose the mono, complement, triad and so on. Can anyone direct me to a blog post which explains the reason why there are so many options to chose from; or the "good way" to use the color while

Thanks a lot

4 Answers 4


In a nutshell, primaries are colors that are themselves. The secondary colors are constructed by mixing two primary colors.

Complementary colors are typically on opposite sides of a color wheel and are the ones, when mixed together, create gray. In the real world of color, few pigments are pure, so you usually get a brown.

When you mix all primary pigments, you get black. (With light, you get white.) Again, in the world of pigments you don't actually.

Any book that talks about meanings of color are selling you paper.

  • mixing all primaries gives you black. (in theory. In reality, it's a muddy brown, hence the need for adding K to the CMY printing process)
    – DA01
    Mar 16, 2011 at 14:23
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    thanks, I like the explanation. though what do you mean by the last sentence "Any book that talks about meanings of color etc are selling you paper." - that they are not worth reading??
    – aurel
    Mar 16, 2011 at 14:24
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    @aurel: yeah, pretty much. There are studies which are suggestive, but these findings are so overstated and piled upon by nonsense that they are worthless. I suppose one can derive some inspiration from such things, but be aware of the tenuous basis in fact.
    – horatio
    Mar 16, 2011 at 14:28
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    There is nothing wrong with using your vision for selecting colors. I don't see any reason to memorize the color value of anything. You will have a different opinion on color next month anyhow.
    – horatio
    Mar 16, 2011 at 14:45
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    Instead of additive and substractive and theoretical etc colors I like to think of what the device outputting these colors does. So if you print in yellow ink you are actually printing an area that absorbs ALL other colors but reflects only Yellow. So adding inks of other colors means you are absorbing more light. Endresult: if you print all it gets black. On the other hand a monitor screen emits light. where yellow is just that: just yellow light. to get other colors you need to add them. i f you switch on all lights you get white. If you turn off the lights it gets dark.
    – leugim
    Mar 16, 2011 at 16:01

The primary colors are called primary because there's no way to create those colors from mixing other colors.

Secondary colors are created from the mixing of the primary.

Red + Blue = purple.

But Purple + green != blue.

As for how to use them, this is something google can easily help with. Google 'color theory' and you'll find all sorts of resources.


Any three colors can be used as primary colors in a given color system (http://en.wikipedia.org/wiki/Primary_color). For light, red, green and blue are usually used because they give the widest range of possible colors (gamut). For inks, cyan, magenta and yellow give the best results.

Equal parts of two of the primary colors and none of the third give you a secondary color. You can even define tertiary colors (equal parts of one primary and one secondary).


This is very informative article on this


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