Blue plus yellow gives green or bluish yellow (usually called greenish yellow) or yellowish blue (usually called greenish blue). These are grayed by a small amount of red or any color containing red, as orange, purple, brown or gray.
Red plus yellow plus blue give—
(1) One of the above if any one or two of the three is present in the small proportion necessary for graying purposes.
(2) Gray if all three are present in such proportion as to neutralize each other. If this is perfectly accomplished we have a neutral gray, otherwise a red gray, yellow gray, blue gray, purple gray, etc. Gray intensified becomes black, and there are modified blacks, as blue black, green black, etc. In making up a gray or black, beginners usually err in taking too large a proportion of yellow, and perhaps also of red.
(3) Brown if the three are present within certain other ranges of proportion. Browns may be classified as yellow browns, red browns, blue browns, green browns, purple browns, etc.
There are all gradations between neutral gray and the browns; between the browns and the secondary colors, orange, green and purple; between the secondary colors and the primary colors, red, yellow and blue.
In the practical handling of dyes, in order to get the entire range of colors from the primary colors, it is necessary that the red, yellow and blue dyes chosen be pure and luminous in color quality. Fortunately, there are such dyes.
There are, however, other valuable dyes that do not have this purity of color. For example, there are yellows containing considerable red or brown, reds containing yellow or blue, blues containing red, etc. Then there are dyes that are green, brown, purple and black. All of these have limitations when used in compounding colors. Neither a yellow inclined to the brown, nor a red containing blue, can be used to form a luminous orange. Likewise the compounding of a vivid blue green, or reseda green, forbids either the yellow or the blue containing any appreciable admixture of red.
All of these dyes find great use in the industries, and all of them, within their limitations, are valuable for color mixing. Having acquired a working knowledge of red, yellow and blue dyes, it will be found of practical benefit to include some of the others. An experienced craftsman works with a small range of colors chosen for his particular purpose.
Dyes differ in coloring power, even different specimens of the same dye, so that it is not possible to give quantitative formulas for certain colors bearing popular names. It will be helpful to discuss a few of them.