Whether it is legal to shoot a BB gun in Colorado depends on the specific location.
Although BB guns operate differently from firearms, they are considered "deadly weapons." Therefore, Nevada state law still forbids their use or possession in many of the same circumstances.
It is a crime in California if a person intentionally shoots a BB gun at another person, per California’s assault and battery laws. This holds true even if a person shoots at someone else and misses. Depending on the specific facts involved in the shooting, the shooter could be charged with: battery, per California Penal Code 242 PC, assault, per California Penal Code 240 PC, or assault with a deadly weapon, per California Penal Code 245(a)(1) The penalties for these offenses can include both extensive jail time and substantial fines.