As more and more instruction becomes "interactive" with hyperlinks, flash animation, and graphics tablets, I think students will prefer the interaction with traditional paper and the visceral feel of physically coloring their answers. On some level, color must heighten a learning response as most of us have been conditioned to stop at a light.
The coloring book is a simple 5-minute warm up for the students to get them ready for your lecture or instruction. Having this ready for the students as they come in the door will allow you to take attendance and deal with issues that arise at the start of every class.
I welcome any feedback you wish to give.