The blue areas are possibly false colour associated with bright stars, and not unusual with achromatic lenses, or possibly, blue wavelengths associated with some stars. Some of the faint pink areas are possibly nebula. The dark areas may be dust. Star colours are probably not representative, but close - not sure - value the feedback. The image may be a little over saturated.
This is
a good starting place for camera settings and astro photography - not specifically Pentax, but can be adapted.