Limited Palette Methodology. By Don Finkeldei:  A structured way of thinking in terms of   temperature, value, hue and saturation using gray moderators. 

Definitions:

1. Color Temperature: The colors visible to the human eye range  from red to violet (red, orange, yellow, green, blue and violet).  Red is warmer than orange, orange is warmer than yellow but cooler than red, etc..  Generally,  a neutral gray with a little more red, orange or yellow is considered a "warm gray".  A neutral gray mixed with a little more green, blue, or purple are considered "cool grays".  Artists also have to think in terms of relative color temperature between adjacent  brushstrokes.  For instance, an orange gray stroke is cooler than a red gray stroke next to it even though they are considered both warm colors.  This is very important to remember.  An example is a green hill that slopes up, then levels out at the top under a cloudless blue sky.  Since the sloping part of a hill receives less light from the blue sky overhead (slanted plane) than at the top of the hill (horizontal plane), the color at the top of the hill must be cooler than the slanted side of the hill.  That's accomplished by adding a little more blue to the green and lightening the part of the hill that turns from slanted to horizontal.  Think also in terms of relative color temperature.  You can have either a predominantly cool painting, or you might have a predominantly warm painting... but the relative color temperature between objects, planes and brushstrokes still need to be observed.

2.  Value:  the lightness or darkness  in terms of grays going from black to white.  Of course, you will be painting with color (red, yellow, blue, etc.)  .  A higher value is lighter, a lower value is darker.  If you could remove the color (like a black and white photo), then, you see the value scale in terms of black and white.  You can actually do this in Photoshop.  Try it.  Take a picture of your painting.  Turn it to gray scale and look at the values that way.  You'll be amazed how color fools your judgment. That's because the eye is most sensitive to yellow in middle of the color spectrum.   Remove the color and you'd see the true value.

3. Hue:  the attribute of color that enables an observer to classify it as red, green, blue, purple, etc., and excludes white, black, and shades of gray.

4. Color Saturation : The intensity of color.   For instance, pure cadmium red straight from the tube has a higher color saturation than if you mixed a neutral gray with it.  Mixing a complimentary with a primary color will also decrease the color saturation.  See The Color Wheel for complimentary value explanation.   For instance, mixing red with green.  Green consists of yellow and blue.  So, you've actually  just created a gray.  To an artist, gray is any combination of red, yellow and blue.  Neutral gray is composed of equal  parts of each.  Color can be slightly grayed and hardly noticeable as a gray to a flat neutral gray with no hue color at all.

The Methodology:

Using the basic primary colors cadmium red, cadmium yellow,ultramarine blue, white and premixed grays is the basis for limited palette painting.  See the article "How to Mix Grays for Use with a Limited Palette".  There are several advantages in using a limited palette:

•  Color harmony is automatic.  There are various theories on color harmony.  Basically, color harmony is mixing a little of all the colors with each other.  Since grays are premixed from the primaries and  gray is used to modify value and color saturation for about everything you mix, color harmony is built in.
  
  
• Changing hue, value and color saturation becomes more predictable.  You'll have much more control when modifying your tube paints.
  
  
• Mixing paint using the basic primaries plus grays naturally forces you to think in terms of the attributes hue, value, color saturation and color temperature instead of just picking a color that's close and modifying it with other colors and white without thinking much about the color attributes.  You'll become a "one stoke" painter much faster if you think and compare these attributes on a stroke by stroke basis with the rest of the painting.

If you're just starting to paint you might think that having a large array of tube colors on your palette is good.   It's not.  You should refrain from using a large color array palette until you have mastered the use of a limited palette.  This takes years.  A limited palette forces you to learn the logic of color mixing.  After you become experienced in mixing what you want you'll most likely find that you really don't need all those extra colors anyway.  

Most beginning artists usually think in terms of color only.   A good experienced painter looks at a color and breaks it down into it's attributes by by asking:  What value is it?  What hue is it?  How much color saturation does it have?  What's the color temperature?  All of these attributes are critical in a painting.  Does it fit the local, meaning how does the next stroke of paint you're mixing fit with the strokes of paint next to it.  For instance, Mountains in the distance shift to a bluer hue, lighter and closer value range, and color saturation becomes less.  You wouldn't want to use a blue that's as strong as a blue object in the foreground.  How is this accomplished?  Well, you could add a little white to the blue.  Or you could use the complimentary color (orange) to dull the blue, add a little white, keep going back and forth until you get the right color. 

By thinking in terms of hue, value and saturation, and using gray moderators you can approach the right paint qualities you need much faster and with greater accuracy.  For instance, if I determine that the hue is right, it's just has too much color saturation (too strong of a blue), all I need to do is grab some of my premixed "neutral gray" of about the same value and mix with the blue.  If I judge that the value is too low, I'll use a higher value neutral gray with the blue.  If I judge that the value is too high, I  can use a lower value neutral gray.   If I want to make the blue a little warmer, I'll use one of my warm grays.   If I want to change the hue slightly from a blue to a purplish blue, I might use a touch of red in the gray (or added to the blue, but I find adding it to the gray first, then mixing that with the blue is much easier).  

The point is that a good painter always thinks in terms of the paint attributes of hue, value, color temperature and color saturation instead of just "what color is it".  AND, how it fits in with the rest of the painting.  Many great painters don't use a limited palette or premixed grays.  That's ok, They've learned how to master a  lot of colors and know exactly what they need.  I just happen to like the logic and simplicity of using a limited palette with grays.  It's much simpler to understand and control once you start thinking in terms of color attributes rather than just color.