I pre-ordered an HA Green, but I want to purchase the lightbulbs before it comes. Can I use the Zigbee lightbulbs as regular lightbulbs until the HA Green arrives? or will the lightbulbs automatically go into pairing mode and flicker?
Depends on the bulb. Philips Hue for instance work fine as a dumb bulb if there is nothing to pair with. And (at least some) have Bluetooth so you can connect them that way to your phone in ther interim.
There is no set rules, and will depend on the bulb. But I had a few for a while that I just used as dumb bulbs until I fixed my setup.
When powered ON, any unpaired Zigbee bulbs will indicate they are in paring mode by a single episode of blinking or cycling through colors or color temps. They should only remain in pairing mode for a few minutes - and won’t go into pairing mode again until next time they are powered ON.
Hopefully you also ordered the SkyConnect dongle when you ordered the Green? The Green itself does not have any radios.
It definitely depends on the brand bulb. I know ikea bulbs don’t automatically go into pairing mode, so they will work fine as dumb bulbs. I can’t speak for other brands though.