Additive and Subtractive Mixing
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Activity 3: Color Mixing
Why?
 Ever since kindergarten we are taught that red paint and blue paint swirled together
makes purple but it’s never really explained why this color transformation occurs. So
how do colors mix? It may appear that colors meld together magically to form a new
hue but in reality the observed result is due to mixing in either subtractive or additive
processes.
Learning Objectives
 Understand the concepts of Additive and Subtractive Mixing.
 Be able to discern the resultant color when various pure and impure color lights or
pigments are mixed.
New Concepts
 Color mixing
Vocabulary
 Subtractive mixing
 Additive mixing
 Pure and impure pigments
 Subtractive Primary colors
 Additive Primary colors
 Cyan
 Magenta
Visible Light Review
When white light passes through a glass prism the visible spectrum emerges
in the rainbow we name as red – orange – yellow – green – blue –
indigo – violet. These colors are actually the various
wavelengths () of pure light from 400nm to 700nm that make
up the visible spectrum.
http://www.greatreality.com/ColorComp.htm
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
Additive and Subtractive Mixing
2
When white light enters a material the color perceived is the result of the material absorbing all
visible  except for the apparent color which is reflected. For example, when light strikes a
piece of red paper, the chemical constituents of the paper absorb the shorter  corresponding
to green and blue and transmit or release the longer , those corresponding to red. For each
pure spectral color, a reflectance curve indicates when light is released or bounced off of a
material.
www.sabic-ip.com
Why is fluorescent light often
considered to have a “cool” hue?
www.candle-web.co.uk
So, what occurs when the illuminated material (as is the case for
most paints, inks and dyes) is not spectrally pure? How is the viewed
color being generated? It is often assumed that pigment colors are
adding together to make a new hue when actually the reverse,
subtraction, is the case.
Subtractive Color Mixing
Subtractive Mixing is a method of generating color occurs when white
light enters a solid medium. Depending on the chemical nature of the
material, certain  of light will be absorbed (ie. “subtracted” or removed from consideration).
The remaining  are refracted (bent) and reflected yielding the color perceived. The
components in a colored material are not usually “pure” meaning that they absorb all but one 
of light. Therefore colored materials are “impure” meaning the  range transmitted covers
several of the colors of the rainbow resulting in a mixture.
If a paint is made of blue and yellow pigments, what colors are absorbed? What
colors are reflected?
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
Additive and Subtractive Mixing
Primary pigments are those three colors that when combined produce black (ie. all light is
absorbed). The primary pigments in Subtractive Mixing are as follows:
Yellow
Cyan – “blue-green”
Magenta – “red-blue”
www.horrorseek.com
Complete the column in the table below with the correct color of light for the  Absorbed.
Primary Subtractive
Color
Yellow
Cyan
Magenta
 Reflected
 Absorbed
Apparent Color
Red , Green
Blue, Green
Red, Blue
Activity
Using provided white paper discs and colored paint provided, paint one disc blue and one disc
yellow. Set these aside. In a palette with indentations, mix some of the blue and yellow
together. Take one additional white disc and paint it with the result of the mixing. Explain the
results of painting all three of the discs in the table below:
Disc number
Color Observed
Explanation (colors absorbed)
1
2
3
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
3
Additive and Subtractive Mixing
4
Additive Color Mixing
The making of color with light as the medium follows a different pathway called Additive
Color Mixing. When examining the process of coloration by an additive method, the medium
involved is wavelengths () of transmitted light superimposed on one another such that the
colors combine or “add” together to make a new  or new color.
Primary pigments are those three colors that when combined produce
white light. The primary pigments in Additive Mixing are as
follows:
Red
Blue
Green
www.horrorseek.com
A demonstration of Additive Mixing would occur if beams of colored light were shined upon a
white wall. If the beams were shined adjacent to one another their separate colors would be
seen. If the beams are subsequently superimposed, the original colors would “add” and a new
color would appear.
Activity
Gather 3 students/group and using flashlights with colored gel covers (red, green & blue), follow
the procedure below.
1. The first student projects the red light onto a white wall.
2. The second student separately projects blue light and then the third student projects
green.
3. Lastly, have each student overlap their light source with ⅓rd of the others.
What color is at the center? Why?
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
Additive and Subtractive Mixing
5
For each primary color a complementary color exists which when combined with the
primary results in grey, black or white. The complementary color results for Additive &
Subtractive Mixing are shown below:
Colors Yielded
Additive Mixing (ie. lights)
Subtractive Mixing (ie. pigments)
Red
--------------
Cyan
white
black/grey
Blue
--------------
Yellow
white
black/grey
Magenta
white
black/grey
Green --------------
http://www.greatreality.com/ColorComp.htm
For generating Subtractive Colors through the use of pigments or inks, any color can be
produced by mixing correctly proportioned amounts of cyan, yellow and magenta EXCEPT for
a true black. In this case a true black pigment must be added as the mixing of cyan, yellow and
magenta often yields a muddled black.
The CMYK color printing model utilizes cyan, magenta, yellow
and black inks instead of mixing the first three to remove all
light hence make black. This method is called 4-color printing
and is more appealing visually by producing a true black.
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
Additive and Subtractive Mixing
The following illustration demonstrates the production of color by both the Additive and
Subtractive Mixing methods.
www.quickstep.com
Activity
Using the supplied paints and colored filters on flashlights, demonstrate each of the following
examples and complete the table below:
Mix
Resultant Color
Red paint + Blue paint
Green light + Blue light
Red light + Blue light
Magenta paint + Yellow paint
Magenta + Cyan + Yellow paints
Red + Blue + Green lights
DONE!
Written by Dr. Shari Litch-Gray, Chester College
in collaboration with Dr. Cheryl Coolidge, Colby-Sawyer College
Additive or Subtractive?
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