NorthSouth,
some mil, police or med copters have special anit-collision lights to fly with night vision glasses. I think you have seen such an anticol light. But I only know green ones. Perhaps an answer.
There´s a picture - that shows Bavarian Police EC135 on the fin after the red anti-col a blue one
http://www.flugzeugbilder.de/show.php?id=616800