Here is the latest:
I was not happy with the sky. It was too grainy due to the texture of the paper. The color was good, just grainy. See the image below.
So, I burnished the blue with a white pencil. This requires bearing down on the pencil with a heavy hand while being careful to avoid previously colored areas. The burnishing with white maintained the color while smoothing out the graininess.
I also wanted to add some more depth to the color in the monkeys. I have already used 3 or 4 colors in the image below.
I used a reddish, brown pencil to highlight a few areas; for instance, the monkey's haunches and tail, as below.