The website RadioReference is the place to go to find out frequencies and agencies for just about anywhere in the US.
And there are notes about encryption and sometimes pending system changes.

Most of Colorado first responders are on an 800 Mhz trunked system. Some agencies haven't converted yet and others keep the VHF freqs as backup for areas where the trunked system doesn't have coverage. But the dominant system in Colorado is the 800 Mhz DTRS.

Each area is different so it would pay to investigate one's area closely rather than relying on general internet advice.

ARES/RACES in the ham bands cannot, by regulation, be encrypted.