Congratulations on the great camera!
Here is what I suggest. Go to the Menu and select colour space to be sRGB and the raw file format to be DNG, not PEF.
Thing is, raw files are not just "files." The pef or dng is a container, it contains raw data that the sensor recorded (which is not a photo yet), along with metadata (date, aperture, shutter speed, copyright data if you input it), preview thumbnails (that is why the thumbnail on the camera and in explorer can look different from the raw file once you open it in software), and even post processing information.
Post processing is actually like developing film. To open the raw file (the dng, for example) you will need software that does this. Some software merely "previews" the raws - you do not want that. You want software like Silkypix, Lightroom, Aperture, or FastStone (there are a couple threads with lists of good raw editors). These will interpret the raw data and turn it into a photograph. Software can have its specifics, so different software might render the same raw data a little differently. And then you develop/post process it - you adjust brightness, add contrast, change saturation, make the white balance just right.. Different software does this in different ways.
If this is your first DSLR, you might want to just shoot jpeg for a while and learn about shutter speed, ISO, and aperture. These three parameters let you manipulate things like photo blur, depth of field, brightness, etc. You see, jpegs are raw data that gets processed in-camera according to the way Pentax engineers designed it. Its not perfect, because the algorithms are merely machines, they do not know what is beautiful. But they are not terrible either. They are a fine place to begin. One more thing.. jpegs are already developed raw data, but they also discard a lot of information. That is why editing jpegs is usually a bad choice, but processing the DNG file is much safer, as the raw data remains unchanged and nothing gets lost - you merely change how it gets interpreted.
Also! You might want to read
this. Maybe even bookmark it. Good luck