If you use Silkypix as supplied with your camera, here is what I would do (and do myself):

Set sharpening to: no sharpening
Correct lens distortion if needed
Set Development quality to 99 (default=80)
Go to NR settings and set all values to zero, then play with the very top one (color correction) until most of the color noise is gone.

Develop to jpeg and sharpen (edges, no surface sharpening as that will increase noise again). There will remain a grain like noise but alot less color noise (including the yellow blotches).

My other way of developing RAW is using the ADobe DNG converter which shows less of these colored blotches by default after converting the RAW to DNG. The reason why remains a mistery. Next I open the resulting jpeg in Irfanview (or Photoshop for that matter) and use Neat Image plugin to get rid of color noise. If you have Neat Image, I can send you the profile I currently use for the FZ18.

The upside of the latter method is less color noise remaining in the final image and a little finer grain as a bonus. The downside is that the process consumes more time and the colors (especially reds suddenly look very different) need alot of tweaking to match reality, whereas Silkypix does a good job retaining settings as used by the camera if you don't change them. Also, Neat Image does take away a little bit of the fine detail where Silkypix doesn't.