That law is likely unconstitutional, as a violation of free expression. Business owners still has their constitutional rights in how they wish to run their businesses.
I’m on the side of businesses who wish to minimize their risk by not taking in counterfeit bills.
Colorado is an anti-Constitutional state.
It’s my understanding that most businesses that don’t accept cash don’t refuse it because they are afraid of counterfeit bills... it’s because the employees can just pocket the bills.
The local ball park in our town is that way. No cash, only charge or debit cards. Or else electronic payments.