At that size, I imagine you're already operating across several states, and HR already has processes in place to deal with differing regulatory requirements. Adding the latest CO rules to these processes isn't all that onerous in the overall scheme of things. It's not like "post a minimum salary" and "post listings internally" are crazy or complicated ideas.

I can't see why the number of employees or companies complicates this. I work for an enterprise with over 60,000 employees and they have decided to apply the Colorado standard to all job openings.

Editing This was poor word choice in the morning; I should say I can clearly see how the size or scope of a company could complicate this. I just don't have any sympathy for them; you adapt your processes to match the desired state.