Desaturation, or faded colour, is actually the most common visual distortion people report experiencing in dreams, by and large though, the visual appearance of dreams tends to look very much like reality. So why then, might you experience a commonly recurring thematic setting?
There are various different interpretations. If you were looking for a psychoanalytic explanation, you might say that the desolate scenery in such dreams represented a repressed sense of isolation and was perhaps a characteristic of depression. A more modern, neurocognitive explanation, would be that such recurring scenery has arisen from two avenues. Firstly from the input of whatever media you're intaking throughout the day, people who play a lot of video games, for example, will have more frequent dreams around fantasy or video game characters, with more prevalent themes of action. The same can be said of that kind of scenery.
Secondly, there is a feedback aspect. If you wake up having had a particularly vivid dream that involved such desolate scenery, and then expressed surprise or curiosity about the scenery, perhaps taking the time to recall it in the morning, the strength of that memory is increased and reinforced. Thus, the next time you dream, that memory is more likely to be activated again during another dream, generating the same scenery and further reinforcing the association.
These are oversimplified explanations of course, and all, some or none of them may apply to you, but it's nothing to worry about. There is really no deeper meaning to such scenery in the context you've provided. Generally speaking, the characteristics of most people's dreams tend to fluctuate, some dreams are very bright and vivid and colourful, others are more washed out, others are blatantly abstract - such fluctuations are absolutely normal, although the if most of your dreams are uncoloured or desaturated then it can be trained out to a certain extent.
