This is a detail from an abandoned steam engine in a National Park in Alaska.  The park is called Hatcher's Pass, this engine was used to power the carts that went into the mountain side to pull out the ore. 

We were quite high in the mountains, and the light was bluer than normal. The shadows were very interesting because the sun is low in the sky.

I used two colors for the entire painting, Thalo Blue, and Burnt Sienna.  I don't count white as a color.  At the very end, I applied a little Cadmium Yellow to the rusty area.  Color can be much more interesting with a limited palette.