"Realistic Navigation" - yellow light

[Freelansir]

Recently I wanted to learn more about "realistic navigation" and so I flew the B-25 blind landing practice provided in Single Missions.

Everything went smooth but I got a yellow light enroute to the target field. It looks like some kind of marker beacon. However it only blinked on briefly once. I understand the concept of Outer/Middle/Inner beacon markers.



I searched the internet but all I could find is this gauge, but without a light associated with it.



http://en.wikipedia.org/wiki/AN/MRN-1

So my question is, what in the world is the yellow light for ?

Thanks