Markers and pens are two great options for working with coloring books.

Even though they produce a solid color, they can be fun to experiment with.

Check the link above to learn the basics of this medium.

Start with laying out the tools that you are going to use.

Decide on a color scheme.

If you are not sure - use the color reference page for my coloring books (here) or a tutorial on how to choose colors (here).

Don't forget to check out my tutorial for markers and pens techniques (here).

Backgrounds are a good starting point as they usually set up the mood for a design.

If it gets too much to color with one color - there is no "coloring police" to stop you from switching to other design elements.