Warning: Have you put an LED in your tricolour?

Last night I went down to SYH to take a look at Kalessin's tricolour & bicolour navigation lights. The result was frightening, and if you have put a white LED bulb in your yacht's tricolour, you should probably be frightened too.

At the Southampton Boat Show the Cruising Association did a demo of what happens when you put an LED bulb in a bicolour or tricolour light. I didn't actually see the demo, but in the past week I have spent many very slightly frustrating hours working with members of the Regulatory and Technical Services committee (RATS) trying to concoct a diagram which demonstrates what happens, for Cruising magazine.

Here is our current version:

In fact I am not 100% sure that there is an LED in Kalessin's tricolour, but given the effect, I hope there is!

From the starboard side, the light appears green - the tricolour is the correct shade, the bicolour definitely bluish. From the port side both lights appear to be the proper shade of red.

The frightening bit is the view from straight ahead. The tricolour appears, approximately, white. Through binoculars you can see that there is a green bit to starboard and red to port, but the effect is as if the coloured filters don't quite meet in the middle, which is not the case.

Apparently this is caused by two things, mainly:

• The light of an LED bulb comes from around its edges. The light of an old-fashioned filament bulb, with a vertical filament in this case, comes from the middle.
• There is no such thing as a white LED - it's a combination of yellow and blue light which our eyes see as white. 

I now have to decide whether to spend £50 on a multicoloured LED lightbulb (which RATS doesn't really approve of), or anything up to £200 on a proper LED fitting, or £10 on a new filament bulb whose only real disadvantage is that it uses about five times as much power as an LED and of course you only use the tricolour when you are getting no charge either from the engine or from solar power!