Unless you pass light through a prism and spread it
out, you cannot tell exactly what colors, or wave lengths,
are in it. Something
that appears red to the eye may prove to have some orange
and yellow in its spectrum, as well as red, for example.
Color wheels, or hue circles, show the relationship
between the various colors.
They are nothing more than the visible spectrum bent
into a circle. The
hues are arranged in the same order as they come out of a
prism, that is according to wave length.
The one exception to this arrangement is purple and
violet, which do not actually appear in the spectrum because
they are a mixture of red and blue rays.
However, to form the completed circle, they are
arranged in the proper order between the blue and red.
According to Sir Isaac Newton, between the visible
violet and the visible red are indigo, blue, green, yellow
and orange. As
our study of color progresses this appears a limited
concept, as the solar spectrum contains only seven of the
multitude of colors that we are familiar with, to say
nothing about the colors we are not familiar with.
There are infinite numbers of colors that we cannot
infra-red and ultra-violet we know something about – rays
that are invisible to the eye but can be demonstrated by
various instruments. Then
there are the “odic” colors or the psycho-magnetic
colors, which many with sight know exist.
In the pigment color chart normally used, the six
basic colors of the rainbow are shown: Red, orange, yellow,
green, blue and violet.
A seventh line could be added for indigo, between
blue and violet.
According to the Brewster theory the primary colors
are red, yellow and blue; the secondary colors orange, green
and purple; and the tertiary colors russet, slate and
secondary are called secondary because by a combination of
two of the so-called primary colors, one of the secondary
colors can be produced: red and yellow produce orange;
yellow and blue produce green; red and blue, violet.
The triad of tertiary colors is made by combining two
of the secondary colors: green and violet produce olive or
slate; green and orange produce citrine; orange and violet
Seven, page 2
From the polarity scheme described in the chromatic
curve, red, yellow and blue are very convenient as primary
colors, as red is exciting, blue is cool and soothing; while
yellow is the medium color or the center of the luminosity.
The hues red, blue and green have a very important
property. If we
mix the right amount of light of these three hues, we can
match closely any hue on the color circle.
For this reason, red, blue and green are often called
primary colors. There
are other sets of three hues that
have the same property, but the red-blue-green set is the one that is used most often.
Color Wheel #2
The lines join
Yet another variation of spectral colors is shown in
the following table. We
are presenting for comparison the views of several
scientists, - all experts in the field of color - and views
they sometimes seem, for color carries a personal as well as
scientific connotation, so there appears no absolute
Complementary Spectral Colors
Green light mixed with purple light also produces
white or gray. This
pair has not been put into the table because purple is not
considered by this source as a color of the spectrum.
Purple light is a mixture of red light and blue
light. So a
mixture of green light and purple light is really a mixture
of three spectral colors.
seven, page 3
One way of defining complementary colors is that a
complementary color is the color a normal eye will see when
closed after staring at a given radiant color.
If the person stares at red they will see a greenish
blue with the eyes closed.
If they stare at orange they will see a deep blue.
If at yellow, a color between blue and violet.
If they stare at greenish yellow, they will see a
purple; and if at green, they will see a magenta.
If they reverse these colors and stare at
greenish-blue, they will see red, and so on.
The reasons for this phenomenon seems to be that
certain of the rods and cones in the retina, which are in
tune with the color that is stared at, become fatigued and
call up a sympathetic action of the nerves not acted upon.
This sympathetic reaction will show up in from 10 to
60 seconds depending upon the radiance and the individual.
There are many mixtures of light that look white or
gray. Some of
them, like those reflected from a gray surface bathed in
sunlight, include all the colors of the spectrum.
There are others that include only two colors.
Two colors which produce white or gray when light of
these colors is mixed are called complimentary colors.
Such colors set each other off and serve especially
well for purposes of contrast.
Scientifically, complementary colors are based on
wave length. Any
two surface colors (such as dyes, paints and inks) are said
to be complimentary if, when mixed, they cancel each other
out and produce a neutral sensation such as gray or black.
Mixing light of different colors is not the same
as mixing paints. For
example, every artist knows that a mixture of blue and
yellow paints looks green.
Paints, dyes and other coloring materials are able to
take away certain wave lengths from the white light that
falls on them, leaving only some of the wave lengths to be
taking-up of certain colors is called absorption.
If you mix the proper amounts of paints of all
possible colors, you get black paint.
Each kind of coloring matter in the mixture absorbs
its own set of wave lengths and nothing is left to be
that reflects very little light of any kind looks black, and
anything that reflects a mixture of many different wave
lengths looks white. Black is not a color, but the absence
of color, or the absence of reflected light.
Pigment soaks up certain color waves and reflects the rest of them. When you see a red building, or a red cloth, the pigment in the paint and the dye absorb all of the colors except red. Thus red is reflected to your eyes. A paint pigment is named for the color that it does not absorb. Plants look green because the material in them takes up almost every other color, and only the green is reflected and reaches your eyes.
The flakes of “coloring matter” in white paint
may not be white at all.
Under a microscope, these flakes may look as clear
and colorless as glass, but because they reflect day-light
so well, the paint looks white.
Snow, which consists of colorless crystals of ice
looks white for the same reason.
seven, page 4
colored light, you add colors, the additive process.
In blending pigment color, the subtractive process
What happens when a blue filter and a yellow filter
are placed one after the other in the path of a beam of
white light? The
blue filter removes or subtracts from the white light
all of the red and yellow light that is in it.
When a painter mixes two pigment colors together, he
is subtracting colors. The
pigment in each color is like a filter that removes some
colors from white light.
Mixing the pigments is like placing one filter after
the other in the path of the light that strikes the paint.
When a blue spotlight and a yellow spotlight shine on
the same white surface, this kind of mixture is called additive,
because it is made by adding one kind of light to another.
Additive primaries are said to be red, green and
blue. One color
wheel uses orange, green and blue.
This is based on mixing actual light rays, adding
colors together. As
white is the effect produced by all colors of light shining
together, there will be a space of white at the center where
the colors blend.
Color filters transmit light, but strain out certain
colors and let others pass through.
Most filters are made of glass, gelatin or plastics,
and these work by taking up part of the light passing
through them. Traffic
lights are a practical example of their use.
Most of the things we see around us are opaque and do
not allow light to pass through them at all, all the light
that falls on them being either absorbed or reflected.
If the object absorbs some colors and reflects
others, then it looks colored.
Its color is the color of the light it reflects just
as the color of a filter is the color of the light it
Colors are classified in two major categories:
achromatic colors – these include black and white, and the
whole series of intermediate grays, varying only in
brilliance; and chromatic colors (of the spectrum) that vary
also in hue and saturation.
(Greek “Chroma”: color)
Value or brightness is the difference in the brightness
or luminosity of the same colors within each hue – this
correlating with the energy of the stimulus, i.e. the
amplitude of the wave.
the purity of a color.
A truly pure color is free of any gray.
Saturation or purity is the quality of
brilliance or cleanness, as opposed to drab or dirty, and is
dependent on the mixture of short and long wave lengths.
Monochromatic wave lengths give the purest
Tints, shades and hues are often spoken of
indiscriminately, but this is not correct.
seven, page 5
When we combine a color with white, we produce a
variation in the brightness of the color, called a tint.
When we combine a pure color with black, we produce a
variation in saturation or purity, called a shade.
By mixing a color with its complement, we can also
darken it without changing its hue.
When we combine gray (which is a mixture of black and
white) with a color, we produce a tone.
the printing trade:
The subtractive primaries as used by printers are
cyan, magenta, and yellow.
The complement of red is blue-green called cyan.
The complement of green is a red-purple called
The complement of blue is yellow.
Another variation of color compliments as outlined by
In this color wheel, the complementary colors fall
directly opposite each other.
In surface colorants such as paints, inks, and dyes,
the fundamental or primary colors (according to Herbert
Paschel) are magenta, yellow and cyan.
They are called primary because every other color can
be produced by mixing them together in various proportions
or by adding white, gray or black to them.
By overlapping circles of color, it can
be seen that a mixture of equal parts of magenta and yellow
produces red; a mixture of cyan and yellow produces green;
and a mixture of cyan and magenta produces blue.
The mixture of all three colors in equal parts
Where color dots are used side by side as colorants
(in printing) a surface made up of a mixture of equal parts
of magenta and yellow appears red.
When white light strikes it, the magenta absorbs
green rays from the light, and the yellow absorbs blue rays.
Since both the magenta and yellow reflect all the red
rays, the surface appears red.
Cyan and yellow produce green because the cyan
subtracts the red rays, and the yellow subtracts the blue
rays, and both reflect the green rays.
Since magenta absorbs green light, the cyan absorbs
red rays, only the blue rays remain to be reflected from
seven, page 6
The world is colorless to some people who are called
optical nerves do not react to color.
It is generally accepted that the world was colorless
to prehistoric man who was color-blind.
The faculty to see color has developed slowly over
Color blindness is the inability to distinguish
between certain colors.
Genuine color-blindness, or complete inability to see
colors, is quite rare, affecting only one person in 300,000.
What is more generally inferred by the term is some
form of color-deficiency, the most common of which is the
red-green confusion which affects about 8 million persons in
the United States. There
is no known cure, but it is not troublesome.
Due to the commoner red-green color-deficiency, most
traffic lights have been changed from red and green to
orange-red and blue-green, colors which are more easily
Many tests have been made to find out what
combinations of colors are easiest to see.
This knowledge is useful for signs, posters, license
plates, traffic signs, etc.
The visibility scale is as follows in order of
Black on yellow
Green on white
Red on white
Blue on white
White on blue
Black on white
Yellow on Black
White on Red
White on Green
White on Black