Colorado dog bite law
Strict liability state
The owner is generally liable for a dog bite even with no prior history of aggression — there is no "one free bite" defense. Comparative fault and provocation can still reduce or bar recovery.
Whether a claim succeeds usually turns on this classification plus a few facts: where the bite happened (a dog owner is generally not liable for trespassers provoking the dog on the owner's own property), whether the victim provoked the dog, and — in one-bite-rule states — whether there is evidence the owner knew the dog could be dangerous. Comparative fault rules can also reduce recovery if the victim is found partly responsible.
This is a general reference, not a determination for your specific facts — confirm how this rule applies to your claim with a licensed attorney in Colorado.