I've noticed that most of my Metal Halide lamps have been flashy today upon start up. Bright pink flashes from my two remaining little 20w CMH's
in my bedroom, and bright orange flashes from most of my six QMH's in my garage. I wonder why that is? It's very noticeable each time it happens.
I know for a fact that it'll be even more noticeable once I finish installing the final two wallpacks in my garage. (Eight total once I'm done.)
So sometimes during start up they'll simply warm up without any flashing, but other times, they'll flash pink, (bedroom CMH's) orange, (garage QMH's)
until they've finally finished warming up.
My Sylvania QMH's flash orange the most violently, at least so far it seems that way... longer orange flashes.a. but they also take the longest to
reach full brightness as well.

I’d have said at first its just the halides being pulled into the arc stream, but I’ve actually, (albeit very rarely), seen mercury arcs pull a tiny pink orb into the arc too!
Wonder if it’s tiny pieces of glowing electrode coming off?

I've noticed it is quite random. Sometimes, there is lots, and sometimes there is none. I have lamps that flash a lot and some that almost never flash. Sometimes the flashes are long and intense, other times they are brief and not too bright. I've even had some flash after running for a few hours (although less intense).

When I was in high school, the 400W halides in the gym would each flash once. They would warm up to the clear mercury phase, stay like that for a little bit, and then have a single, intense, bright pink flash that lasted about 1-2 seconds before fading. When it did fade, the lamp acquired its normal colour (sort of like a signal to the end of the warmup period).

Strangely, I have noticed, like suzukir122, that when one lamp flashes, it seems like the others do as well. Like they all flash or none flash. I also noticed it with preheat fluorescent that are all on the same switch. Sometimes they are blink-happy and sometimes they barely flash, but it seems like all the lamps on the circuit do the same at the same point in time.

It's weird because sometimes the flashing colors with my QMH lamps seem either pinkish orange or orange. The flashing in the ones at my gym class were orange all the time, and they would flash normally in twos or threes, before fully warming up.
The flashing with my 20w CMH are always pink, never orange... which makes me wonder about my CMH Philips lamp for my Wallpacks.
I've seen that lamp flash before warming up... but the flash from it was purple, and very slight. I have never seen that lamp do any orange flashing yet.