Taking sketches to the next level

Yesterday at lunch, I drew these 3 thumbnail sketches.  Each one took about 2-3 minutes.

This morning for a warm up, I figured I'd paint them into quick colour-comps.  I started by fixing the borders of the drawings and converting to pure black and white.

After that, I spent about 25 minutes in total painting.

Supposed to be late evening in the forest, just before the sky turns colour for sunset.  These were all painted on one layer, with one brush (the standard chalk brush in Photoshop with transparency and brush size turned on.)  The point of these is not to have finished paintings, but to be able to see a little better what colour and lighting would do to the locations.