In my opinion, all pen programs should reset the device's colors to standard
before starting.
I was unable to convince the people who wrote "ctekpen" of this point of
view. As a result, if you run any of the demo files that fiddle with the
color table all of your plots after that will be messed up.

The reason to have it the way it is is so that you can change the shades
of the primary colors beforehand to "customize" your plot.

The routine for mapping RGB notation to what the Tek wants doesn't work
very well.

This code assumes that you have the "raster option". If you don't,
ctekraster won't work.

Authors: Jeff Thorson, Glenn Kroeger, Michele Debiche

- comments by Joe Dellinger
