Back [to Color in 'Vision and Invention' by Harlan]
The Color Wheel and the Natural Order of Colors - The Afterimage - The Primary, Secondary, and Tertiary Hues - The Achromatic Scale - Color Terminology - Chromatic Gradations: Tints and Shades - Chromatic Whites and Blacks - Broken Colors - Chromatic Grays: Warm and Cool
[From: Harlan, Calvin. Vision & Invention, An Introduction to Art Fundamentals. Englewood Cliffs, NJ 07632: Prentice-Hall, Inc., 1986.]
Few colors from the tube may be considered absolutely correct in every way for all 14 colors on our wheel--primaries, secondaries, and tertiaries; yet some may require less adjusting of value and chroma than others. The blues and violets, as well as the greens, are usually too low in value when taken straight from the tube. The reds, except alizarin crimson, are usually not far off in value. The pure yellows and oranges are usually even less out of pitch.
First of all, choose a red [say, a cadmium red, medium] that seems to be neither too light nor too dark, nor too warm [red-orangish] or cool [over into crimson]. Add a bit of another red [another cadmium, light or deep] to make it lighter or darker, if absolutely necessary. Every precaution should be taken to avoid contaminating any color. Every color must retain its native brilliance unimpaired. This means that no black nor any amount of a broken color, such as the siennas or ochers, may be used. It is also inadvisable to use white to lighten the value of any of these 14 colors, as white tends to cool certain colors.
Yellow is easily muddied. To obtain the right yellow for the top of the wheel, compare the two or three pure yellows in tubes for relative lightness and warmth. The final choice must contain no trace of orange [red semi-chromes] or green [blue semi-chromes]. Try a cadmium yellow, light, Lemon yellow, so-called, is too greenish. Medium yellow may be too into the orange-yellow zone.
Choose a blue for your primary blue [two steps up the wheel from violet] that is not too light [it should be darker than turquoise, green-blue, just above it on the wheel], not warm [containing no red semi-chromes, as does ultramarine blue, directly below it on the wheel], nor cool [containing no hint of green, as does turquoise]. Try one of the pthalo-cyanine blues or something similar, often given the name of the manufacturer [Grumbacher symphonic blue, Winsor blue, and the like]. Names aside, what one wants is a true blue.
All this requires patience and careful looking--and funds for the requisite number of good colors, preferably designers' colors, or what is often called gouache. It must be kept in mind, where the primaries are concerned, that red, theoretically, is only red, yellow is only yellow, and blue is only blue. The secondaries--orange, green, and violet--are [ideally] the results of a perfect blending of two of the primaries: Red and yellow produce orange, yellow and blue produce green, red and blue pr produce violet--or so they should. But no pairing of these colors, even if the paints are of the finest quality, will result in secondaries of full intensity. A good, strong violet, for instance, is almost impossible to obtain by mixing even the best red and blue paints.
[Pigments do not always blend the way reason says they should, because they are made of a great variety of substances, and they are mixed or ground with a variety of vehicles to transform them into paints.]
I strongly recommend that, beginning with this study, large color swatches be made of every color and every mixture of colors. These will form a handy collection of colors for some of the work to follow. There are, of course, other colored papers available, both expensive and cheap [Color Aid, colored construction paper, and the like], that may be added to the collection. I also recommend that the light in the room in which all color work is done be daylight or a light that simulates daylight.
When all 14 hues have been obtained, a fine adjustment may be required in order that each hue may assume its proper place in the natural order of colors around the wheel. In arranging the hues from top to bottom of the sheet, the primaries [yellow, red, and blue] could appear as large circles, the secondaries [orange, green, and violet] as medium-size circles, and the tertiaries as small circles. Or one may prefer circles, squares, and triangles of about the same size. [In any event, it is advisable that all of the hues be cut from swatches, rather than painted on directly, if only because many comparisons and alterations of value and even hue may have to be made.] A good idea, for these and other studies, is to draw the shapes with pencil and ruler or compass, paint the shapes slightly beyond their boundaries, then cut them out with scissors or mat knife. It is not of much importance whether or not the warm colors [the yellows and reds] be placed along the right side of the wheel or the cool colors [the blues and greens] be placed along the left side.
To complete the wheel, as a psychological wheel, we must draw spokes form each hue to its complementary.
The wheel may or may not be asymmetrical. There are at least two reasons for making an asymmetrical wheel:  It allows one to establish, a bit more accurately, the location of each of the hues from top to bottom the position of the cool colors vis-Ã-vis the warm colors; and  it allows one to place the reds, orangey reds, and yellow at the farthest distance from the hub of the wheel so that their more extroverted, radiant, expansive energies may be emphasized, and it allows the more introverted, contractive blues to be placed nearer the hub. The result is a more dynamic image or diagram, as a symbol of the chromatic compass should be. In addition to the above, it invites a movement of the eye along the path of receding and advancing hues [clockwise into depth from violet, then forward through orange and red, and so on]. [pp. 94-95]
[Harlan, Calvin Vision & Invention, An Introduction to Art Fundamentals. Englewood Cliffs, NJ 07632: Prentice-Hall, Inc., 1986.]
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