Rainbow Windmill

Another day of dull, flat light and no opportunity to be anywhere other than work!
I bought this little gadget at a panotomime (oh no she didn't!, oh yes she did!) and thought it would entertain the grandchildren - oh yes it did that alright!
So today, I have blipped it.
It was interesting varying the shutter speed and seeing the different colours that became dominant. There may be some physics behind that but it's way above my understanding.
Maybe some better opportunity tomorrow....!