Short Answer.
In Colorado, you generally cannot reopen a car accident claim after settlement once you sign a release and accept payment. Exceptions are rare and usually require fraud, misrepresentation, or mutual mistake. See whiplash legal options here.
Example
If you settle a crash claim for $75,000 and sign a full release, you cannot later seek more money—even if your injuries (like whiplash) worsen—unless you can prove the insurer engaged in fraud or both parties had a significant mutual mistake.