How to understand lighting cables?

There is more than one possibility - depending for example on whether your lights were provided with earthing.
One possible and plausible scenario is:
One live ( red or brown) cable going to ceiling rose.
Two neutrals (black or blue) - one coming into the ceiling rose from the previous light in the loop and the other leaving it and going to the next light in the loop. (These two will be connected to teh same neutral terminal).
One earth (green or green/yellow striped) for earthing light fitting.

J
April 2008