@Braden-Hallett That's a really good question. Before I did this, I would have done night scenes using purples or grays, but was surprised that she really stuck to pretty saturated blues that were mostly of the same hue but in different values. Her whole piece used an extremely limited palette -- although I did it digitally, if I had been doing it in watercolor, I could have done it all with just a cool blue and a warm rust (and the yellow at the window). Even the owls were a very light value blue and rust. Colors are more muted at night so that would make sense.
Design-wise, she didn't use any perfectly straight lines which is something I struggle with all of the time. I tend to want to over-control my lines which leaves things stiff.