Fountain colour changing light

Colour changing pond light, how did they work? We have found a picture of an old style colour change light 

As you can see the light is clear and there is a disc divided into 5 colours (some discs were 4, some 6 colours)  The disc has small "ridges" on its perimeter edge. These ridges are there to give resistance to a small jet of water (not shown) which by pressure pushed the disc around.

There are several problems with these discs. You need a reasonably powerful pump to operate one AND a nozzle, but if you were a pond owner and brought one (They do look nice)  They often get clogged with algae within a few weeks so not only would they not turn as well as they did the colour would soon be lost. Often the discs would too easily break. You only need to break one small piece and the wheel can no longer rotate. (Since if a segment is missing it can not push past this) They are very seldom seen these days.

Today you can now buy LED lights which can produce millions of colours and hues