Two things are required for this: A webcam and a Kuando BusyLight. The idea is that the BusyLight will change it's colour based on whatever object you put in front of the webcam. If you put a green object, the BusyLight will turn green. If you put a blue object, it will turn blue, and so on.
Available here: https://www.youtube.com/watch?v=REesqP77meQ