"legal tender for all debts" Colorado doesn't need to pass another law, the US already says that you have to take legal currency. I did find one liquor store that refused to take cash during the pandemic for health reasons. I complained to the cashier but they haven't changed their policy.
I also know of a small Italian restaurant that gives you a 10% discount for using cash.
Thomas Sowell: There are no solutions, just trade-offs.
