Your Legal Right to Switch
Under Colorado ethics rules, clients generally have the right to discharge counsel at any time, with or without cause. The retainer agreement does not eliminate that right, though it may address fees or costs for work already performed. If a firm says you are permanently "locked in," get a second opinion from another attorney.
The terminated attorney may assert a lien on the case file for fees and costs already incurred. In practice, this is often resolved at the time of settlement: the new attorney and the old attorney negotiate how the contingency fee is split based on work performed. You do not typically pay out of pocket for this. The total fee you pay usually remains the same (33% or 40%), with the two firms dividing that fee between them based on their respective contributions.