After the sketches are finished, each section is colored in contrasting flat colors to that of its adjacent neighbors. This makes it easier to select individual sections later on for coloring and shading.
Then, each selection is individually colored and shaded.
And finally, a sections are blended together to remove hard edges and are given any final touch ups.
It may seem like a lot of effort for something that will never appear more two and a half centimeters tall, but sometimes it's those little extra details that count the most.