China grade crossing signals have steady blue light beneath.

[Robert_Gift]

The blue light, now often beautiful rich LED blue, indicates that the signal has power and is working.
It also coincidentally is excellent at making the railroad crossing stand out well among the background light and clutter, especially at night.
When the signal activates and the red lights flash, the blue light goes out.
(I'd leave it on.)
When all lamps were incandescent, were they saving electrical load (draw) by turning off the blue lamps during signal activation?
A crossing will have just three lights facing each direction. (Not another pair of lamps facing backwards on the other side of the track as in the US.
....X
(o)-(o)
...........(o)

The cross buck reads:
Be careful, fire car (locomotive)

A sign beneath reads:
Red Signal, Stop Car
No light, don't use. (No blue light, signal is dead.)