I thought about her question and really listened to the sounds to which she was referring. They weren't quite crickets, because the sound was continuous, not short bursts. It sounded more like the drone of cicadas. The more I listened, the more I thought to myself that the droning sound was very similar to the sound masking static to which I continuously listen while at work. It was actually a fun revelation for me. No wonder why I find long hikes in the mountains so relaxing. The continuous sounds of mother nature (like those cicadas, the wind rustling leaves, and babbling brooks) become natural masking "noises" to me.
I guess if I had to associate a "color" with those sounds (since they sounded like the hissing of white noise or brown noise), I'd have to call it "natural." LOL! :-)