During the day, no lights are required (but you can use lights as you would during the night). At night, signal Fz1 must be displayed, which is one white marker light near the buffers. Using all three lights as you would on a mainline move (Signal Zg1a) is also permitted though, and this is what everyone actually does these days. In fact, if during shunting you pass over a level crossing that doesn't have active protection, using all three lights is mandatory day and night. You don't need end of train markers or anything for shunting, so you can just have Zg1a or Fz1 on on both ends and save yourself the faff of changing the lights whenever you switch direction.
This seems to have become the norm, as far as what I've seen in freight yards lately. Especially on locos with older-style lightbulbs like the 363 and 294, I could imagine it also slightly extends the lifespan of the bulbs.
That makes sense, since the worst stress on filament bulbs is when you turn them on. Personally, I usually do Zg1a on both ends when I'm shunting with a big mainline loco, but in the 363 Fz1 on both ends just feels better somehow.
I was told by a BR294 driver, though I might be misremembering (because I was more focused on the physics data ) that Fz1 meant that you would turn on the headlight (and taillight iirc) closest to the station building, or if there is no station it would be the right in the direction of travel. So for example if you are shunting at Mainz-Bischofsheim and facing north you would have the right headlight/taillight turned on.
So, even if you are pushing the carriages forward and the locomotive at the rear of the train, there is no need to turn on the red lights?
Yes. PZB should be turned off but Sifa stays on (quite a bit more complicated in real life, but that's the gist for the game). You really shouldn't turn on the red lights. The red lights are for proper train movements, not shunting movements. That being said, EMUs/DMUs often have red lights at the end while shunting because that's how their software works (no driver at the desk = red lights, essentially). But on locos, you should have the 3 white lights (Zg 1) on at both ends (if not coupled). The one light described above (Fz 1) is rule-consistent, but I have barely seen it used in real life. Zg1 is the de facto norm.
Though if you don't enable PZB in game, you won't get a platinum medal, so if you care for scoring, shunting with PZB it is (even though it's not prototypical). Turning off SIFA would require you to break a lead seal IRL and some more rules to follow, a good indication that you're not supposed to even turn it off frequently but only in certain uncommon situations.
Thank you very much. This is what I appreciate about this forum—that you can learn such useful little things there. I certainly noticed that the G6 has a maneuvering mode on the light selector. which turns on white lights at both ends, but you never know, the developers made a mistake...
