CO doesn't have required safety inspections-- unless you've recently built a car or truck(primarily rods)and go to license them. You need to have them inspected by the state patrol or a state licensed inspection station for safety and vin number and they then attach a tag to the car if it passes--by law.
Many get around this if they have the CO title in hand and just take the title in to the DMV and license the car in that manner...but I've been told that if there was an accident or incident the owner could face a stiff fine/loss of DL and the vehicle could never be licensed again.
And all officers have the discretion to ticket/impound a vehicle if they deem it hazardous/unsafe.
If you bring a non-CO registered vehicle in all you have to do to get it licensed is get a vin inspection...go figure