Check your sidelights from dead ahead. You should see both red and green. However, by moving toward one side just 1-3º you should then see only one light. If you still see two lights, an approaching vessel won't be able to tell which direction your are going.
My take is that these are the sidelights. I was looking for something that showed a rule as to length and maybe an additional set of sidelights required. I didn't find it, and it's my bedtime, so I'll leave it up to the team.*
I would add that if the sidelights were much further aft, it would be very difficult to see both from dead ahead.
-- Edited by Carey on Monday 7th of March 2011 12:11:07 AM