120. In the study of color and its application authorities differ so materially that it is not only impossible to reconcile their theories, but the different terms used to express color thought create inextricable confusion.
121. One authority fixes the neutrals as being black, gray and white; another regards them as those hues or tones which lack definite color, like quaternaries. Authorities differ, moreover, upon even the fundamental principles. Chev
122. One must remember always in studying color that we are treating with the material, not with the illusion. We are dealing with pigments, not with prismatic phenomena, and it must be obvious that the only three primary colors that can be used in a way to produce all other colors are red, yellow and blue.
123. Whatever may be the spectrum theories of Sir Isaac Newton, Young or Helmholtz, for practical reasons we prefer to follow an authority as eminent as Chevreuil, for years the head of the National Gobelin Works of France, and a man experienced in the practice as well as the theory of color. Any effort to fix the character of color and describe it by periods and epochs will always prove unsatisfactory, for the reason that terms and expressions have changed with every period since the Egyptian, 4000 B.C.
124. We think we know purple until we discover that the purple of royalty, the ermine and purple, the purple of the cardinals’ robes, frequently approximated what we now call carmine. Royal purple and Venetian blue are mere trade terms. Practical men in the purchase of things decorative soon discover that color terms convey only individual impressions and no distinctive qualities that may be relied upon; so that any effort to fix the color value by periods would be futile. We may assume that in the age of oak, mahogany, white and gold or walnut furniture, the fabric and wall colors harmonized with the wood colors, and to that degree we may fix the period character of color. The moment that the tone of the woodwork or the light conditions varied, color character varied also.
125. We must also bear well in mind that colors which have come down to us as examples of ancient times have been subjected to the changing influences of centuries, and have faded and altered. The colors on the walls of the historic rooms of European palaces have greatly altered. The flat reds and the deadish blues of the Pompeiian frescoes have been altered by chemical action during the 1,850 years’ burial under the lava of Vesuvius. We are not justified in judging of the colors of A.D. 79 by the restoration-examples in 1900. Hence the mere expressions Pompeiian red, Pompeiian blue, can convey no definite, positive meaning.