that just in accordance with the degree of
purity of transmitting power of a pigment will be the purity of the
color which we get by its use. But absolute purity of pigment we
cannot get, so we cannot deal with it as we do with light, and we deal
with a practical fact rather than a scientific fact, as painters.

=Primaries and Secondaries.=--As all the other shades of color are
produced by the combinations (over-lappings) of the waves or
vibrations in the light rays from the primary colors, we have a series
of colors called secondaries, because they are made up of the rays of
any two of the three primaries: as purple, which is a combination of
blue and red. When dealing with _light_ the secondaries are: shades of
violet and purple from red and blue; shades of orange red, orange,
orange yellow, yellow, and yellowish green from red and green; and
bluish green and greenish blue from blue and green--the character of
the color being decided by the proportions of the primaries in the
mixture.

These conclusions have been reached mainly through experiments in
white light. The primaries so obtained do not hold good with pigment,
as I have stated, but the principles do. It will avoid confusion if I
speak hereafter of the combinations as they occur with pigment, it
being borne in mind that it is a practical fact that we are dealing
with rather than a scientific one.

In dealing with _pigment_ the primaries are red, blue, and _yellow_,
not _green_. Of course the secondaries are also changed; and we have
purple and violet shades from red and blue, orange from red and
_yellow_, and green from blue and yellow--all of which vary in shade
with the proportion of the mixture of the primaries, as is the case
with light.

=Tertiaries.=--Another class of shades or colors is called _tertiary_,
or third; for they are mixtures of all the three primaries, or of a
primary with a secondary which does not result from mixture with that
primary. Tertiaries are all _grays_, and grays are practically always
tertiaries. If you keep this in mind as a technical fact, it will help
you in management of color. Grays are, to the painter, always
combinations of color which include the three primaries. The usual
idea is that gray is more or less of a negation of color. This is not
so. Gray is the balancing of all color, so that any true harmony of
color, however rich it may be, is always quiet in effect as a whole;
that is, grayish--good color is never ga