What I have met, the interior lights just had their own switches, separate one for the front one or two and then one for the rest. So it was mostly up to the driver, how he operated these lights.
I was keeping them ON within the city area, where the sops were frequent and passengers were shuffling all the time, when there was sufficient road lights, I even left the front ones on. But when departing to the outer stretch of the lines, where there was longer drive between stops, I turned them OFF about a minute after departing the stop and ON again about a minute before arriving to the next one, to allow passengers to get seated or ready to leave. The front ones I then turned on only when at the stop and only if someone was using the front door (the busses had at least 3 or 5 doors, the front ones had quite narrow corridor around the driver cab, so people tend to not use them that much).

The glazing on insulators makes the surface smooth, so it is less tendency to hold moisture and contamination on its surface, so less risk of a flashover.
What the different colors mean, if anything at all, I have no idea.

Blackened arctube.

Sadly, I do not have access to a car, currently. So I am mainly looking for places I could buy off of that can ship it to my door.

I have a normal clear glazed (white) porcelain mogul socket, but I also have a yellow one. I have also commonly seen pink and gray ones floating around on Ebay. Why would they go through the effort of putting colored glaze on the sockets? What benefit does it serve? I thought maybe it could be an indicator of PSMH or HPS, but I see them used in situations where that doesn't make sense. Any thoughts?

Edit: Now that I think about it why glaze them at all? It it even necessary?

You might find some on Facebook Marketplace.

Anyone know where I could buy online 700-series tri-phosphor or even halophosphate F32T8 lamps? Maximum price is $6 per bulb.

The lens of my tracklight is made from regular soda lime glass. It would break in the case of arctube explosion.

If it’s a genuine track light for halide, I’d guess it’s designed to contain a tube rupture 🤔

@RRK
Very interesting theory, this would certainly make sense. I remember when I used to start up my 400W diazotype MH lamp that it would flash a lot before finally stabilizing. I first thought maybe it was just particular to that lamp, but I haven't had any other MH lamps to compare it to so maybe they all do that. Interesting

My idea is MH lamps typically have some amount of halide salts condensed on the electrodes. When the lamp attempts to ignite, these salts evaporate immediately and  fill the arctube with metal and halide ions. Halide ions seems to be quite good at quenching the discharge, likely by intercepting electron avalanches. So you often see when MH lamp flashes first on ignition, then goes out, then makes a few repeated attempts and only then establishes the arc. That way, igniting MH lamps needs some insistence with a dense series of ignition pulses having a certain energy. More, usually a presence of some open circuit voltage with rather low impedance is required to be applied together with ignition pulse series. Certain lamps even need a capacitor of a few microfarades that will discharge to the electrode gap at start to do glow-to-arc, automotive or entertainment electronic MH ballasts or ballasts for short-arc mercury lamps are including this!