I tried to print something in color using a Samsung CLP-300 laser printer using foo2qpdl driver.
Printer accepts Cups job without any error messages, but no print comes out of the unit.
Changing printing mode to black/white works well.
I tried the same action with the latest Ubuntu 9.04 (end of march version) with success at color mode.

Is it a ghostscript issue, or so ?

I don't know. I don't really have time to mess with this issue so I just installed Samsung's UnifiedLinuxDriver * and it's working fine on Bluewhite64, a 64 bit clone of Slackware. When I tried to extract and manually install the PPD driver for the CLP-315 from Samsung's driver via CUPS, I noticed that the printer would work for a bit and then spit out a totally blank page. Does the foo2qpdl driver support color on a Samsung???? I'm not sure whether the current version of Gutenprint supports color lasers such as the CLP series from Samsung yet. Anyway, other than some problems with Sansung's current driver, the CLP-315 now works in most cases.

* Beware!

I use it on slackware 12.1 with my clp-300 and one test I did with current output the test page ok. I'll have to test it again.

Did you download the icm file during the install?

Hmmmm.... I tried using Samsung's Unified driver as the base for extracting the PPD files necessary for CUPS. I was wrongly under the impression that the foo2qpdl didn't support color yet. I stand corrected and I'm in the process of downloading and installing the foo2qpdl driver with its associated ICM files for the CLP-315. I appreciate you pointing me in the right direction. Since I'm using Bluewhite64 CURRENT, I'll probably have the same problem as the OP who's using Slackware CURRENT. Anyhow, I appreciate the information on the foo2qpdl driver... thanks again.

Hmmmmm. After installing the foo2qpdl driver, I'm honestly thinking that installing Samsung's Unified driver is probably cleaner even with its problems. I intend to proceed with the installation of the foo2qpdl driver so I have both options available to me in the future. At this point, Samsung's Unified driver appears to be a much cleaner installation except for scattering the .gnome-desktop and Desktop directories everywhere....

***PS. I've installed the foo2qpdl driver and it indeed only prints in monochrome. In the color mode, the CLP-315 just clicks for a bit and then stops with NO paper feed or eject. BTW, the foo2qpdl installation isn't THAT bad as the driver allows for a pretty thorough un-installation via make uninstall ... On BW64 and presumably Slackware, one has to manually create the /usr/share/foomatic/... directories so the installation of foo2qpdl is complete. Other than that, one just uses the web interface for cups to administer and setup CUPS. As far as the OP's problem, I don't know as I have the same symptoms with foo2qpdl, i.e. no color, but monochrome is ok.