to be those made from the colors in use, and out on the palette, rather than by the substitution of others. They are more in unison with the scheme of color, and consequently harmonize better.
A manufactured gray is mad warm or cool in proportion to the amount and quality of color introduced. Red and yellow are lively tones, and produce warm tints, while blue in predominance is excessively cool. Violet is an intermediate tone.
In Theory, the three primary colors, red, blue, and yellow, in a given proportion, will counterbalance or neutralize each other ; but with mineral colors, seldom more than two are requisite to produce a satisfactory gray. A good example of the first principle is a mixture of carmine, silver yellow, and ultra-marine, which can be made to have either color predominate.
Apple green and carmine make a soft, pearly tone, very delicate in quality, and useful when combined with pink. Either deep red brown or violet of iron, combined with deep blue green, forms a somewhat stronger tint, and is useful to shade blue flowers or drapery. It is also good for clouds and distant effects.
