... but just for British ships as due the German Imperial Navy it was forbidden to send out signals at light, except an absolute emergency case.
This has lead to the loss of the Black Prince, which had made a mistake on a turn due the night fights and went through between two german battlelines.
On my HMS Velox there is such a fighting light mentioned in the plan, sitting on a single rod midships. The "fighting-lights" had been also ment for entering ports due wartimes, as they had been locked by portable mine-barriers and nets to avoyd any Submarine or fast Torpedoboat attack.
When entering the port at night, they had been asked for their identification. After it was checked the barriers had been removed and the waiting boat had permission for entering.
The lights had been a mixture between red, green and white lights which had to be given in a certain line, but had been just hardly visible, with lower intensity as the standard signal-lights.
Just my penny- hope it was out of any help.
Jörg