KIds need to be taught that coloring is not a race. The more time and effort you put into your picture, the more valuable it is. The key to coloring is these four things: Go slow and steady, stay in one direction, stay in the lines and color in solid leaving no gaps in color.
Here are some other posters I created along the same subject.
Weight of Great Coloring
Slow and Steady Wins..
Hard Work Beats Talent
Work is like Cupcakes...