Third Grade - Color Mixing bottles, jars, and vases

Third grade has a huge color theory unit.  We are just getting underway with the concepts.  Everyone drew and traced shapes for bottles, jars and vases.  The 3 catches: each had to have an opening at the top, be symmetrical, and overlap!  The overlapping was key.  Each object was painted with the primary colors, but when they overlapped they had to be painted with the secondary that the 2 primaries would mix to make.  Puzzling you say?  Not for KBK's third grade!