20 Color Standards and Nomenclature. 
Chroma .—Degree of freedom from white light; 
purity, intensity or fullness of color. 
Luminosity. —Degree of brightness or clearness. The 
relative luminosity of the spectrum colors is as follows: 
[Yellow (brightest) ?] , orange yellow; orange; greenish- 
yellow, yellow-green, and green ; orange-red ; red and 
blue (equal); violet-blue, blue-violet, violet.* 
Warm Colors .—The colors nearer the red end of the 
spectrum or those of longer wave-lengths (red, orange, 
and yellow, and connecting hues) “and combinations in 
which they predominate. ”t 
Cool , or Cold , Colors .—The colors nearer the violet 
end of the spectrum or those of shorter wave-length, 
especially blue and green-blue. “But it is, perhaps, 
questionable whether green and violet may be termed 
either warm or cool.” 
Complementary Color .—“As white light is the sum of 
all color, if we take from white light a given color the 
remaining color is the complement of the given color.” 
When any two colors or hues which when combined in 
proper proportion on the color-wheel produce, by rota¬ 
tion, neutral gray, these two colors each represent the 
complementary of the other. 
Constants of Color .—The constants of color are num¬ 
bers which measure (1) the wave-length, (2) the chroma, 
and (3) the luminosity. 
In addition to the terms defined above there are 
many others, for which the reader is referred to the 
chapter on “Color Definitions” on pages 23-30 of Milton 
Bradley’s excellent and most useful book “Elementary 
Color.” 
*Rood: Modern Chromatics, p. 34. 
With the single exception of Vanderpoel '"(Color Problems, p. 28, plates 3, 4, 
where yellow is given first in order of luminosity) all authorities on color-physics 
that I have been able to consult very singularly ignore yellow entirely in their treat¬ 
ment of the subject of luminosity. 
fAll quotations here are from Milton Bradley’s “Elementary Color,” ex¬ 
cept where otherwise noted. 
