Directional terms like that would be confusing in a lot of infrastructure discussions. An outbound firewall rule's "outlist" is the list of things that don't go out.

I want to offer greenlist and redlist

And to those who say this is not inclusive to the colorblind, I say traffic lights

Greenlist and redlist would fail in a global company. Plenty of cultures use red as a color that promotes positivity rather than a negative color. Japan has blue rather than green for their "Go" color. And so on.

I still think traffic lights would work as that’s almost a universal global standard (isn’t Japan the only exception?) and it works well in English

But I think we can agree that the goal when choosing these names isn’t really being concise and easy to use

Well yes, traffic lights are a problem, I’m red-green color blind myself. But the brain is smart enough to supply the right „color“ because it knows that red is on top and green is below. Wait a second, is that offensive towards the color green? ;-)

I've always wondered how you handle those lights at night, if you can't see the enclosure; and how you handle the occasional horizontal traffic light, which my town has one of.

In the context of IP filtering, I would assume those lists would differentiate one-way traffic instead of the regular all or nothing.

I'm still not sure why blocklist wasn't the goto replacement. Depending on your accent, you might not even notice!

In and out doesn’t seem very inclusive, there should only be an inlist!

That’d discriminate against the outgroup. Although I guess “denylist” would be offensive to <whatever> deniers?