There was an exhibition, Day, Light, Night, celebrating the 25th anniversary of Tepta Lighting. They seem to be a company selling (and maybe making, I did not check) lightening equipment. They had some exhibits that it was fun to play with, or just watch. Many changed through time, in intensity and/or colour. This is one of some pictures I took.

This was a fascinating piece, light would change, in intensity, colour, and the number of lamps doing the lighting. The result required some time to take in, but was great.