I remember when I was about 6 years old my parents ran a booth at a local flea market and they would drag me along while they did it. To help curb the boredom that always set in, my parents would supply me with coloring books. Coloring in pages of these books became my favorite way to pass the time. After a while I developed a particular way of doing it. I would trace the outlines with a darker color using strong pressure. Then, I would lightly color in the insides using lighter shades of the same colors. In time I grew tired of regular colors altogether and started to favor the lighter colors.
Now that I am a father myself, I have passed on the joys of coloring to my son. He takes a far different approach to coloring pages. His style would be more described as a speed colorer. He uses a few colors and quickly fills in the general area of the shapes with no real sense of design. It is very hard for me to accept because the golden rule was always stay in the lines. To go outside of my carefully traced lines was to ruin the entire piece.
No matter what there style, I would recomend any parent buys their child a few coloring books. Splurge and buy them the biggest box of crayons that you find. Any expert colorer will tell you that the 8 crayon box does not cut it. The bare minimum is 64. Coloring can be a strong introduction for your child to art and expressing themselves.