I have a 3 bulb light fitting in a bedroom. I want to replace it with a single bulb fitting. I have a new rose etc, but... there appear to be 4 sets of wires coming out of the ceiling, & I think all have red, black & green/yellow wires (its a bit difficult to be sure as there seems to be some additional joining through using a connector). I've looked at another light fitting which only has 3 sets of wires from above. If there were only 3 at the one I want to change I'm sure I could manage to change it, by copying the other one. But what is the 4th one all about? Thanks.