There have been many good posts on color in this thread. Here are some
additional comments.
For color demonstrations, you may want to take a look at some of the
materials I developed that demonstrate both additive and subtractive color
mixing. A lot can be done with just a color wheel and colored
transparencies. And yes, you can make your own transparencies with ink jet
transparency paper and an ink jet printer, as John Denker pointed out.
<http://www.sci-ed-ga.org/modules/materialscience/color/materials.html>
Color is a complicated subject and there are many good references out there.
<http://www.sci-ed-ga.org/modules/materialscience/color/sites.html>
I highly recommend:
Principles of Color Technology, Roy S. Berns, John Wiley and Sons, 2000.
and
Vision and Art: the Biology of Seeing by Margaret Livingstone, Harry N.
Abrams, Inc., New York, 2002.
Given a reflectance spectrum, the color that one sees depends not only on
the peak of the reflectance, but also on the width of the peak and the rest
of the curve as well.
There is no perfect definition of the color "blue." Artists have many colors
with the word blue in them. In my color workshops, I generally state that
our society has to some extent made a decision about the color blue - it is
close to the blue color you select in a computer drawing program when you
select the color "blue."
Standard subtractive color mixing experiments use transparent films. This
is comparable to using transparent dyes or inks. Colors that involve both
selective absorption and multiple scattering, as occurs with many artists
pigments, may give similar colors to ideal subtractive color mixing or may
not.
You can generate about half the visible colors using either 3 primary
additive colors or 3 primary subtractive colors. That is, the colors
generated by mixing either set of primaries (by connecting their color
coordinates and making a triangle) fills about 50% of the CIE Chromaticity
diagram.
To see what are the true complementary colors (not complimentary), just
stare at a color for a long time then shift your gaze to a nearby white
piece of paper. You will now see the complementary afterimage.