Principles and Use of Colors

By Thomas F Abrahamsson

The color subject is very complex due to subtle interaction between the eye-brain system (you) and the physic phenomenon of light radiation. I will do my best to keep this article simple, and I hope you can learn something about the interesting world of colors.

Rays of light...

        Newton (1642-1727) was a scientist and mathematician who is most famous for his theories about how objects move. But he also did some important research about light. He knew that Kepler and Aristotle thought that light and color were not directly related. Both thought color came from white light being changed by an object's color. On the contrary, he also knew that Grimaldi had suggested that light and color were in some way closely connected. As he investigated these two alternatives he performed several light experiment. In 1666, his prism experiments marks the beginning of modern color science.

        He found that if he let white light from the sun pass through a simple prism of glass, it produces a nice rainbow. This would be crucial in his explanation of light. White light was in fact a combination of all colors, and the prism was just used to separate them all from each other. Now, how does this work? Let's begin with some basics:

        Light is an electromagnetic phenomenon, just like microwave waves, X-rays or television waves. By light, we normally mean the narrow range of those waves that are visible to the human eye. This range is called the visible spectrum. Have a look at this chart:

        The frequency of vibration increases to the right, while the wavelength increases to the left. The eye can see light between 400 and 700 nano meters. Rays at 400 nano meters are violet, then we go through the colors of the rainbow up to about 650 nano meters which is read, passing by green color in the middle.

        However, If you are looking at a red wall, this light consist of several different colors and hues of red, where the red is the dominant. Natural light is never completely pure. If we have a lot of light combined, at all nano meter wavelength, we get white light!

        Some artificial light sources are able to create completely pure light of a single wavelength, one of these are the entities popular in Sci-Fi: The laser.
 

What happen when a ray of light hit my eye?

When a ray hits the retina of the eye, which is a light sensitive membrane, signals are sent to our brain to form an image. The retina contains of two kinds of receptor cells, the rods and the cones. The cones are the color sensitive cells. There is about seven million cones in each of our eyes, and they are highly concentrated in a small part of the retina called the fovea. Each cone is connected with a nerve to the eye, allowing us to see great details with the cones. Cones respond to the rays of light corresponding to the wavelengths of the colors Red, Green and Blue.  As a matter of fact, its just these three colors creates the color we see! Since we are able to actually see more than these three colors, there must be some other trick involved. We will soon describe this trick below, but first, lets cover the other kind of cells too: the rods.

The rods on the other hand, are the 'budget cones'.

         In comparison with the precious cones, we have a huge number rods in our each eye, up to 150 million! Many of them have to share the same nerves up to the brain, and they're also muss less effective than the cones. As a matter of fact, they cannot even see color or any fine detail. So, what good do they do then?

         They are very sensitive to low levels of light and can see things that the cones miss. Have you ever look up at a night sky covered with stars, and wondered why you can see some stars better if you do not look directly at them? The cones is the reason. However, we probably didn't get the cones for watching stars, but maybe because they're effective when trying to spot predators and movement 'in the corner of the eye'.

Color models

        Now, what's the trick. How can we perceive hundreds of colors when the cones in our eyes only see three? The trick is to blend these three colors.

Kindergarten color fun...

Do you remember blending colors as a kid?

Have a look at this picture to refresh your memories:

-- Example 1, trying to blend yellow, red and blue water colors

        As you probably know by know, there are three primary colors: Yellow, Blue and Red. These can be mixed to produce three secondary colors: Orange (red and yellow), green (yellow and blue) and magenta (blue and red). Where all three primary colors are combined the result is black. (Or a dull brownish mess, if my memories from kindergarten serves me right).

        Finally, If you go even one step further, and mix the secondary colors with the primary colors you get the six subtle tertiary colors.

         You've most likely seen this model and even tried it yourself using watercolor. This model may work just fine for you, and produce colors good enough. But, you probably now that there is no chance to mix the yellow, blue and red to get white, for example. Trying to mix the colors with your water color set probably leaves a result like this:

-- Example 2, trying to blend some red, green and blue water colors

        - So, how does this work then? To describe the complex model of color mixing more accurately, we have to take a closer look at two two different color mixing models.

The Additive model - RGB

        Additive color mixing is the mixing of projected beams of colored light to form other colors. Many find this model hard to understand, simply because it doesn't work as anything you have learned before. But since additive color mixing is how the eye (and, as a matter of fact, the television set in your living room) produce color, it is an important thing for any artist to know. Have a look at this:

-- Example 3, blending red, green and blue rays of light

         Here, we have three spotlights beaming out the three colors red, green and blue. These are the three primary colors of additive color mixing. This additive model is usually referred to as RGB.

        They can be used to produce four other colors: cyan, magenta, yellow and white. This system is called additive because the three primary colors add up to white. Take a close look at your TV. A very close look, use a magnification glass for example. Each dot on the TV-screen is actually made up of three little light emitters, a red, a green and a blue one. This is exactly how a TV works. If it want to show you a white color, it turns on three of its lights. Yellow is produced by letting the blue light emitter be shut of, and so on. By adjusting the intensity of the light, the full spectrum can be created. (Gray is created in the same way as white, but with less bright light).

        Compare this example 3 picture with the example 2 picture. We have the same three colors, mixing them together, but now, instead of a black blur in the middle, we get white!?. Yes, as a matter of fact we do. This is how the rays of light work to produce color! To understand why we didn't get white in the middle in the previous picture. Have a look at this banana picture.

-- Example 4: A yellow banana, and some beams of light.

        As we see here, red, green and blue light is sent out from the light source (appearing to us as white light), Some rays hit the banana, which sucks up the blue ray. This is why the banana eventually might get hot, as it absorbs the light, but it is also the reason why the banana appears to be yellow. Green and red light together appears to the human eye as yellow light. (See the example 3 picture above).  All yellow items are in fact a terrific absorbers of blue light.

         Items that absorb blue, and about half of the green will appear orange. Items absorbing all red light will look magenta, and so on...

The Subtractive model

        So, what happened in example 2 then? Well, we did actually use something called a subtractive model. By dumping a lot of red, green and blue color in the middle of that picture, we created a spot that actually did suck up all* light that reached it. It sucks up the red beams, the green ones and the blue ones, leaving no color at all. Lets use three other colors. Remember the three colors the three additive model produced: Cyan, Magenta and Yellow.

^*Well--- figuratively speaking. Only the black holes found in the universe does indeed suck up all light, but that's a different topic. Let's pretend that we created a little black hole of our own in example two.

If we used these three colors, and blended them on a white paper, we would get this result:

-- Example 5: The subtractive color model - CMY

        When rays of light are reflected by on a surface, a process of subtractive color mixing comes into play. Because the surface absorbs different colors, this process is referred to as 'subtractive'.

        The three primary colors of subtractive color mixing are cyan, magenta, and yellow which can be mixed to produce blue (cyan and magenta), red (magenta and yellow) and green (yellow and cyan). Notice that the secondary colors of additive color mixing are the primary colors of subtractive color mixing; this is because substances are more likely to reflect multiple wavelengths of light. Very intense blue is rare in nature because few substances will reflect just blue light.

        Printed material in general use these three colors, referring to them as CMY (for cyan, magenta and yellow). Once again, use that magnification glass on a colored weekly magazine and you will find a lot of dots of these three colors. Normal ink jet printers for home PC's also use these three colors to create color images. Usually, a black color is added too, in order to get the shadows really dark) and this color model is known as: CMYK.

Gam out

        So, things are getting pretty obvious now, aren't they? We just add up some simple colors and get a full spectrum of others! Now, let him violently tear down this new world of yours again. Things are, I'm afraid, not quite that simple.

        It is a physical impossible to forming some highly saturated colors by superimposing two others. This is particularly obvious to pure spectral colors, which are themselves saturated. An example of this is that some colors appearing on your monitor cannot be printed, while some printed colors cannot be displayed on you screen! Even worse is that your monitor can show far from all the colors that exist.

         Anyway, Your color video monitor shows its colors because it has three phosphors (red, green and blue) which are activated by an electron beam. That means that the colors you see can only fall within a gamut (space) enclosed by these three colors.

        The chart to the right is an international standard for primary colors established in 1931. I will not explain how this chart is made, and why. (For a good introduction for this, look at Hill Jr., chapter 16). This is an approximation of a so called CIE chart.

         Notice the black polygon inside of the chromaticity diagram. The corners approximately represent the location of the phosphors of your monitor can plot. The only colors you can see on your screen are those that fall within this area! (Just to make this picture look nice, the entire chromaticity space has been filled with color). See appendix A for more information about this chart.

          The CMYK model that we mentioned before is also seen in the chart. If one wants to add the range of printable colors, for example in a weekly magazine, it is possible to use five, or even seven colors to increase the area of the printable color range by up to 20%. This is a relatively new phenomena in the print business. as a

Solution: Other color models
        To handle a seven color system, another method has been used. There are several commercial color systems on the market that do exactly this, for example the PANTONE (r) Hexachome system.

        But, how do we handle fluorescent colors, and silver and gold? Once again, there are several commercial color matching systems available, for example from PANTONE (r) and others. (In a modern Photo shop, go to the color picker and click on the 'custom'-button to see this). With these system, you might get a whole bunch of colored little papers, each color having a unique number. If you want, for example a a nice blue color, this could be named 'PANTONE 285 CVC'. One has to calibrate the monitor as well as the printer to this system, if good approximate colors are to be displayed. At the print press, the same calibration has been made, so you are sure that your nice blue color really turn out to be just that nice on the actual print.
 

Using color when painting

What you need

        In addition to the color tubes, you will also need a decent palette. This is usually a flat pad of paper or thin wood. The paper palettes can consist of layers of thin papers that can be thrown away after a painting session, making these very practical (as there is no palette to clean). To mix colors on the palette, a palette knife (Usually about four inches long) with a flexible blade is used. The tube colors available that approximate the three primary colors mentioned before (blue, yellow and red) are cobalt blue, cadmium yellow pale and cadmium red It's normally recommended to also have these colors available on the palette; purple/blue, light violet, crimson, magenta/red, ultramarine. To this, black and white are added as well.

Pigment

        Color in the To paint is really to distribute the pigment (the color items) onto a surface. These articles of pigment is the main topic when talking about painting. In order to use the pigment to be floating, it must be blended with something else, a solution fluid like oil or alcohol. The color of the pigment can be differ for different solutions.

A short color history

        In the ancient times, only the black (coal), white (chalk) and the natural earth colors were used (red, brown, yellow). The Egypt's added colors from minerals, like cenobite, malachite and were the first to blend organic pigment with inorganic solutions. Back in the middle ages and the renaissance further progress were made. As a matter of fact the blue pigment 'ultramarine' we're extracted from the extremely expensive mineral 'lapiz lazuli'. Lapiz were known from as far back as the 5th century and is found in Afghaniztan mines. The fight for the control of these mines were the cause of man ancient wars. A french and a german were the first to synthetically produce ultramarine as late as in the mid 19th century.

Indish yellow was made from the urine of cows that had been fed with mango leaves.  There was even a color called 'mummy', which was made from actual egyptian mummies that had been balsamated with asphalt.

Other sources of rare colors could be Sepia from octopus, 'dragon blood' from the roots of special palm trees, rubber-ish fluid from a Garciniatree, Carmine from Kochenill insects and so on.

        Several other colors were added the the artists' palettes, like lead yellow and umbra. In the 18th and 19th centuries, the chemical research evolved new synthetic colors and nowadays most collars are synthetically manufactured in chemical processes .

        Modern synthetic colors are superior to the organic ones. They keep their color. they don't fade and also tend to stick to their canvas, even after many years.
 

Mixing color

        There are several ways colors can be used to improve the impression of a picture or to have it make a special 'feeling' for the eye of the beholder.

Warm and cold colors

        Colors can be divided into warm colors (red, orange, yellow) and cold ones (blue, green, violet). The same color can in some cases be warm as well as cold, for example ultramarine is warmer tan Prussian blue. Things that are hot appears to be more close to the viewer, while cold hues are further away. The use of hot and warm colors can be used for many different effects, and different scenes may be hotter and warmer for different reasons. For example, the forest is not always green, in the day its colder, while in the reddish setting sun its more hot.

'Red is hot, is foreground; blue is cold, is background; these are basic truths, which we amateurs use as a crutch all the time '
     -- Miguel Krippahl
 

Complementary colors

Have a look at the circle of color to the right. These is the complementary color wheel. On the opposite site of the wheel you find the complementary color. For example, the complementary color to green is purple. To yellow its blue, and so on.

        You always see colors in comparison to each other, for example complementary colors increases the brightness when placed close to each other. If you blend complementary colors, you end up with brow-grayish colors, and if you place them right on top of each other, they decrease each others the brightness and radiation of light..

        Mixing two complementary colors, will produce gray. For example, you can try to mix neutral grays and browns, and to mix a some of the complementary color in the paint to reduce color intensity.

         A well known way to use complementary color, is to use the complementary color of an item in its actual shadow. For example, a banana on a flat white surface cast a shadow onto the surface. The banana is yellow, a quick look at the color circle reveals a hue a magenta/blue to be its complementary colors which can be used in the shadow area. The example to the left is somewhat exaggerated to illustrate the principle. Also note the use of warm colors in the foreground, and a colder blue in the background.

        As yellow is the most clear and pure color, the yellow light and its magenta shadows are very popular among painters. The magenta shadows further emphasize the yellow in the image.

For a painter, the most important complementary color pairs are:

• Blue -- Yellow
• Orange/red -- Cyan/Blue
• Green - Magenta

        The real master of this was Georges Seurat (1859-91), who unfortunately died at a young age. During his active years, he used all his powers to investigate colors, very very carefully producing a set of very large painting, each one took him over a year to complete. What he did, that made him different was the new theories of his about color. Not only are his motif are timeless and mystic, but its in the technique he used color that is interesting. He built his pictures systematically with a vast number of carefully selected colors, often complementary colors.

The theories of Chevreuls

Complementary colors were known to the middle age artists who used them. For example, they placed light red and green close to each other to improve the color of human hud.

        In 1839, Michel-Eugène Chevreul released a book called 'De la loi du contraste simultané des couleurs', a book about the harmony and contrast between colors. This book was a minor revolution to the contemporary art community as it in easy-to-understand words explained the color theories that the the artists were only dimly aware of. Chevreul presented three simple laws for simultaneous, successive and mixed contrast:

1. Simulate contrast.
Let's have a look at two examples to illustrate the first theory.

 
        This is an example of the Simulate contrast between complementary colors. When two complementary colors are placed close two each other they have influence on each other. The blue color in this example look more yellow, while the yellow area look more bluish.

        Looking at different tones of a color is placed away from each other gives an impression of less contrast. If you place them together, they appear to have a greater contrast: The light area appears even lighter, and the dark area even darker.

 
        When a scale of gray hues are places between each other like this, there is an interesting phenomenon that also belong to the simulate contrast theory. The first gray scale consist of exactly five shades of gray. When placed like this, the gray boxes almost appear to be a little three dimensional, slightly curved. Each rectangle appears to be a little brighter in the right part, and a little darker in the left part. The second picture is a heavily modified version of the first picture where I cheated and manually added this effect with an airbrush to illustrate the phenomenon. The first picture, however, is left unmodified and it's that one you should look at to see this.

         Chevreul suggest that the artist deliberately should paint the border towards a darker tone somewhat lighter so the viewer get the impression of a soft gradient. That is pretty much the inverse of what I did to the second picture with my airbrush. It's important to know that colors placed close (we see both simultaneously, hence the name 'simulate contrast') have a visible effect on each other.

It's also Chevreuls who present the theory that a strong color, for example green, sends out rays in its complementary color (red) on its environment. This is what I did in the banana picture in example two. Note the slight bluish shadow that the yellow banana produce. Blue is the complementary color to yellow.

1. Successive and mixed contrast.
        Successive contrast is, as the name suggests, what happen when we look at different colors after each other. If you have ever been on a sunny beach, improving your tan you have seen this effect in action. When your eyes are closed, you see only red/yellow light (due to the blood in your eyelids). When you open your eyes again, everything in the world appears to be cyan/bluish!

       This color is the complementary color to red! What really happens is that the cones that respond to the red grow tired. When you open your eyes again, only the blue and some of the green cones are alert. Eventually, your red responsive cones wake up and you can see normal again.

        If you stare at a red area for quite a while, and then move your eyes to a yellow area the yellow appears to be greenish because it is mixed with the complementary blue after-image of the red area. This is can be used by skilled mural painters and other very large paintings to create interesting effects.
 

Final Words...

    There are much more to say about colors and their use, bit I will stop here. I hope this article has brought you some insights in this topic.
 

Appendix A: CIE Chart.

Some notes on the CIE chart:

The CIE chart is is an international standard for primary colors established in 1931. It allows all other colors to be defined as weighted sum of the three 'primary' colors . There are no real three colors that can be combined to give all possible colors. Therefore the standard 'primary' colors established by CIE don't correspond to real colors.

Appendix B: References.

One of the actual color circles from Chevreuls (1864):

Appendix C: Some Links

Some useful Links on the Web:

• http://www.andrew.cmu.edu/user/dw4e/color/basics.html

Appendix C: References.

• 'Computer Graphics', FS Hill JR., ISBN 0-02-354860-6, (esp. chapter 16)
• 'Des Colours et leurs applications aux arts industriels', E. Chevreul (1886). . Paris: J. B. Bailiere et Fils.

		The Artist's Handbook A fully illustrated, highly detailed practical guide to painting, drawing, and printmaking. Another top-flight, how-to book from Dorling Kindersley, in the format--and the class--of The Photographer's Handbook. More than 1,000 photographs, drawings, paintings, etc. [More info!]

FARP Article Guestbook Date Name Comment   13 Jan 2004 Anonymous Loading... Very informative and makes it all easy to understand...except that you could use a good proof-reader!! Anyway, good work. 5 Feb 2004 Jessica Johnson Loading... Reply to hella: The only mechanical cows ive heard of are mechanical bulls (like in bars.. See the movie urban coyboy) and "dummies" which are used during the breeding process. But they should have a way to produce a pigment the same color as indish yellow. Take the tube with you to your artist supply store and look arround. To the author: Wow that was good. Extreeeeemly technical. It was like reading a science book or an art history book. Verry helpful. 12 Feb 2004 Vic Loading... great article!!! got more than what i was looking for. i am doing silkscreen printing and plans to use CMYK for picture repro on shirts. think it will work? thanks. 21 Mar 2004 Shawn Loading... wow, all I can say is.... thorough, very thorough.... that and I wish I could spell... Its a very nice tutorial, not only does it tell you what you need to know but also gives you interesting information it might be a bit overwhelming for some however, I almost closed the page, thinking this was not a tutorial but rather a lecture on color. not to say it was dull, the information was interesting non-the-less 24 Mar 2004 Anonymous Loading... Just what i needed, thanks 7 May 2004 Renske bla bla Loading... Nice color explanations, but there is something I'd like to correct: the complementary color to green is RED, to yellow its PURPLE, and to blue its ORANGE... ^-^ No thanx 7 Feb 2005 Punk rock is dead Loading... A lot of info ill admit, but i dropped science last semester lol 13 May 2007 Anonymous Loading... Great article to help those of us studying Art. 27 Apr 2008 Anon. Loading... Thanks, now I hope I can master color. 10 Aug 2008 John Peterson Loading... Thomas - The 3 CIE primaries which your refer to are really the response functions for the eye’s cones. The CIE chromaticity chart is an attempt to describe how the human eye will respond to a given color. The chromaticity chart is notorious for being non-linear. Over the years the CIE has attempted to find a linear color space which approximates equal changes in color. The subtractive color space is the CIE L* a* b* color space. The additive color space is the CIE L* u* v* color space. You might find helpful the Light Measurement Handbook by Alex Ryer at http://www.intl-lighttech.com/services/light-measurement-hand- book kynar Page: [1] 2 3 Not signed in... Sorry, Thomas F Abrahamsson does not allow anonymous comments. Please sign in to write on this Guestbook... Post Message!    Private message?

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