switching between color and grayscale

Is there some command to refresh the system color

    > dictionary?

The color manager is caching color args -> output tuples. The
original question was how to make scripts that can be easily modified
to support switching between color and grayscale. Now you want it to
work interactively from the shell --- looks like bait-and-switch to me

You'll need to clear the color mananger cache

  from matplotlib.colors import colorConverter
  colorConverter.cache = {}