This is one of my favorite activities in MOE. At the link below is our latest Kids Luv Robots coloring book, containing the winning designs selected by our team. The robots are designed and drawn by students up to 3rd grade. We pass out the books at all of our outreach events and demo.
My favorite is Bella, the guinea pig cage cleaning robot. (It's easy to guess that student's household chore!)
http://www.fsrobotics.org/moe365//more.php