Yes, you will be able to register your Chevy Colorado in California. There will be no special requirements or modifications needed to the vehicle's emission system.
There is a difference with California legal and Federal legal emission requirements, however if your Chevy Colorado is equipped with all the Federal required emission components (which it was originally equipped with) it can pass the California smog check and register with the CA DMV; as long as it pass the smog check functional and visual inspections.
The rule is that used vehicles which are equipped with the necessary Federal Emission Components are eligible for California registration as long as their exhaust emissions fall within California's limits and the vehicle emission systems has not been tampered with.
