If a similar experiment is made with the remaining spectrum rays, the
result is always the same: the individual spectrum colors remain
simple, pure colors. _The individual spectrum colors are groups of
simple, pure colors._
[Illustration: FIG. 88.--Violet and green give blue. Green, blue, and
red give white.]
133. Colors not as they Seem--Compound Colors. If one half of a
cardboard disk (Fig. 88) is painted green, and the other half violet,
and the disk is slipped upon a toy top, and spun rapidly, the rotating
disk will appear blue; if red and green are used in the same way
instead of green and violet, the rotating disk will appear yellow. A
combination of red and yellow will give orange. The colors formed in
this way do not appear to the eye different from the spectrum colors,
but they are actually very different. The spectrum colors, as we saw
in the preceding Section, are pure, simple colors, while the colors
formed from the rotating disk are in reality compounded of several
totally different rays, although in appearance the resulting colors
are pure and simple.
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