To reproduce:
1. Start emacs in xterm with "emacs -nw"
2. M-x ps-print-buffer-with-faces
GNU Emacs 23.0.0.21 (i686-pc-linux-gnu, X toolkit) of 2007-05-13
,----[ error ]
| Debugger entered--Lisp error: (error "`ps-default-fg' and `ps-default-bg'
have the same color.
| Text won't appear on page. Please, check these variables.")
| signal(error ("`ps-default-fg' and `ps-default-bg' have the same color.\nText
won't appear on page. Please, check these variables."))
| error("`ps-default-fg' and `ps-default-bg' have the same color.\nText won't
appear on page. Please, check these variables.")
| ps-begin-job(ps-generate-postscript-with-faces)
| ps-generate(#<buffer *posting on gmane.emacs.pretest.bugs*> 669 892
ps-generate-postscript-with-faces)
| ps-spool-with-faces(669 892 nil)
| ps-print-with-faces(669 892 nil)
| ps-print-buffer-with-faces(nil)
| call-interactively(ps-print-buffer-with-faces)
| execute-extended-command(nil)
| call-interactively(execute-extended-command)
`----