C.R.S. § 7-90-807

(1) A foreign entity with respect to which a statement of foreign entity withdrawal has been filed pursuant to section 7-90-806 shall either: (a) Maintain a registered agent to accept service on its behalf in any proceeding based on a cause of action arising during the time it was authorized to transact business or conduct activities in this state; or (b) Be deemed to have authorized service of process on it in connection with such causes of action by mailing in accordance with section 7-90-704 (2). (2) Subsection (1) of this section does not prescribe the only means, or necessarily the required means, of serving a foreign entity with respect to which a statement of foreign entity withdrawal has been filed.