Marco Hemmerling's contribution to Geneva's Festival Arbres et Lumières is a lighttube that constantly changes color, affecting bystanders' perception of their surroundings. We admit, this is the kind of Christmas Tree we'd eagerly have in our living room. [Contemporist]
My grandmother had something similar to this (and by similar I mean not at all...). It was a six foot aluminum tree with a light set a few feet away. In front of the light was a rotating colored disk which would cause the silver tree to look yellow, red, green or blue as it turned. It was pretty psychedelic.