The small size of the sketchbook is a good way to loosen up my hand. I capture the cloudy sky with large colored shapes. I play with a dark Indigo and a dark purple to express the outline of the buildings. I take care to leave some white for the windows and the lights of the night.
When the sun goes down, the atmosphere is transformed into cool colors. The sky and the buildings seem to be in the same shades of blue, so it is difficult to express the depth of the place. That is why I use some orange and red in the windows to create some temperature contrasts.