[texhax] CMYK color v. RGB

[Niall Mansfield]

We've just had a book printed, and there are a few color problems:
more or less consistently, some blues come out looking a little
too green, and others look purple.  The printing company say this is probably due to
the RGB -> CMYK color conversion, and say that we should
ensure images are in CMYK format rather than RGB before
they are embedded in the PDF.

We're using LaTeX, Xfig, GNUplot, Metapost, and all the usual
tools on Linux.  We produce the book as PostScript, and then
ps2pdf that, to send to the printers.

I don't think it's possible for us to use CMYK.  Is it?
Does anyone else have experience of similar problems?

	Thanks,
	Niall

ps: we had advance review copies printed digitally.  They were
     fine; only the litho copies were weird.  The printers say
     it wasn't a problem with their inking of the litho machine,
     and insofar as I understand what they are talking about, I
     believe them.