Typeface colours in postscript

[Edward Lilley]

When I print messages from within Gnus (with A-P), the resulting
postscript file uses exactly the same colours as are used when messages
are displayed within Gnus.
However these colours are generally a bit too close to white to be
legible when printed on ordinary white paper -- is there an easy way to
quickly adjust all the colours in the Gnus face, or am I stuck with
telling M-x customise to never allow any colours in postscript files?

thanks,
Edward Lilley