Many of the figures will also look fine simply in black and white. However for some black and white printers attempting to plot a colour postscript file produces strange results, because the printer interprets each colour as a different dithering pattern. This can be avoided by making a simple change in the header of the postscript file itself.
The header of these colour postscript files contains the line
/SET_COLOUR { setrgbcolor } def
if this is replaced by
/SET_COLOUR { pop pop pop } def
then the plots are rendered black and white.
NB This can be achieved with the aid of the following UNIX command
sed s/setrgbcolor/"pop pop pop"/ colour_figure.ps >! black_white_figure.ps