If you need color PostScript in particular, you can 

	- grab the screen-image using a program which can produce color 
PostScript, such as xgrabsc, xprint, xwpick, and xv

	- grab the screen-image using xwd and post-process xwd into color PS.

You can do this using xwd2ps or the "import" (formerly XtoPS) program from
the ImageMagick distribution. The PBMPLUS/Netpbm package is also good for
this, as is the Xim package.

Also:

Another alternative is to use the Xprinter product from Bristol Technology,
Inc. which provides PostScript output using the Xlib API.  Send email to
info@bristol.com for details.