This is a science exhibit I redesigned for manufacture while a design engineer at the Exploratorium in San Francisco.  The main cabinet houses stepper motors and electronics to control the rotation of 4 levers with squares of colored plastic on each.  The squares are all grey, but in the right light can appear white.  A similar effect happens with the moon itself, which is actually quite dark. 
This was one of my most involved electromechanical projects.  I designed, machined, and built most of the assemblies.  Additionally I designed the circuit boards and coded the microcontroller running the exhibit.