Seeing that I would simply assume they didn't want to advertise specifics about salary, which is not unusual, so they entered 0 into a form. Am I missing something?

Illegal if seen by people in certain parts of the USA.

This seems like an illegal job listing in Colorado.

I've seen a lot of companies "get around" this new law by just saying the job is not available to people living in Colorado, either explicitly on the listing or when you apply.

A cursory glance[0] suggests this only applies if a company has at least one employee in Colorado.

[0]: https://www.natlawreview.com/article/colorado-pay-transparen...

To follow a tangent for a second, this doesn't seem wise on Colorado's part. It doesn't strike me as great law to begin with, but I'm willing to concede that point: the problem is that it creates a considerable regulatory burden for an all-remote company which takes on a single Colorado employee.

As someone who works remotely since well before the pandemic, I'd be pretty upset about this if I were a Colorado resident. I have family in Colorado as well, and while I've never seriously considered moving there this law makes it even less likely.

I suggest that it's not actually $0 but rather they didn't want to disclose the ranges in the form.