Have you gone to the CUPS page (http://localhost:631), to the printer, and
see if there's an option for grayscale only?
Been there. Didn't find that.
Also haven't found a way to do it with lp or lpr.
--
Michael hennebry@web.cs.ndsu.NoDak.edu
"Sorry but your password must contain an uppercase letter, a number,
a haiku, a gang sign, a heiroglyph, and the blood of a virgin."
-- someeecards