4 
Color Standards and Nomenclature 
Till.) These colored disks are slit on one side from 
center to circumference, and therefore by interlocking 
two or more they may be adjusted so that either occupies 
any desired percentage of the whole area, which may be 
very precisely determined by a scale of 100 segments 
shown on the outer edge of a larger disk on which the 
colored disks are superimposed. When connected with 
the color-wheel and adjusted as may be desired, and then 
rapidly revolved, the two or more distinct colors resolve 
themselves into a single uniform composite color, whose 
elements are shown, in their relative proportion, by the 
scale surrounding the disks.* 
The scales (both horizontal and vertical) of the 
present work are all prepared directly from definite 
color-wheel formulae, based on carefully calculated 
curves; the thirty-six pure spectrum hues, represented 
*See the colored figure on the frontispiece of this work, which clearly illustrates this 
method of color measurement. Larger disks of spectrum red, green, and violet are 
interlocked and adjusted so that they present, respectively, 32, 42, and 26 per cent, 
of the circumference ; superimposed on these is a single smaller disk of neutral gray, 
and on this two still smaller disks of black and white, the former occupying 79, the 
latter 21, per cent, of the area. The result of this combination of colors, when the 
disks are rapidly revolved, is that the entire surface becomes a uniform neutral gray 
precisely like the middle disk, which blends so completely with the color inside and 
outside its limits that no trace of division can be detected. Hence, neutral gray 
equals a combination of red 32, green 42, and violet 26 per cent., and also equals a 
combination of black 79 and white 21 per cent. As further illustrating the point, it 
may be mentioned that not only does the above-mentioned combination of the three 
primary colors equal neutral gray but so also does the combination of any color 
(“secondary” or “tertiary” as well as primary) with its complementary, though the 
darkness or lightness of the gray varies somewhat, as the following table shows : 
Spectrum Color. 
Complementary Color. 
Equivalent 
Gray. 
Name. 
Per 
Cent. 
Per 
Cent. 
Composition. 
1 
Black. 
White. 
Red. 
44 
56 
Blue 41 + Green 59. 
72.5 
27.5 
Orange. 
28.5 
71.5 
Blue 51.5 + Green 48.5. 
69 
31 
Yellow. 
33 
67 
Blue 60.5 + Violet 39.5. 
64 
36 
Green. 
51 
49 
Red 57.5 + Violet 42.5. 
73 
27 
Blue. 
64 
36 
Yellow 82 + Orange 18. 
62 
37 
Violet. 
62.5 
37.5 
Yellow 69 + Green 31. 
61.5 
38.5 
