Here is a neat rainbow model that we created with kids during the NCLab Winter Camp at the Discovery Museum in Reno. The rainbow is created using concentric thin rings, removing their halves by subtracting a suitably positioned large cube, and displaying them together. This is also a very good exercise to practice Python lists. We did not use lists with the kids because they were around 10 years old and that would have been a bit too much for them. But this design is just asking for it, so I polished the code after coming home. Here is a link where you should be able to view the code and the design in 3D:
http://desktop.nclab.com/viewer/ac494c819f9c478c9adba43389516af0
Here is a screenshot:
