Currently, Colorado does not require licensure or registration of geologists. Colorado Revised Statutes do require that geologic reports be prepared or authorized by a professional geologist. Professional Geologist is a term defined in Colorado statutes.
The references for these laws are shown here:
34-1-201. Definitions. As used in this part 2, unless the context otherwise requires:
(1) "Geologist" means a person engaged in the practice of geology.
(2) "Geology" means the science which treats of the earth in general; the earth's processes and its history; investigation of the earth's crust and the rocks and other materials which compose it; and the applied science of utilizing knowledge of the earth's history, processes, constituent rocks, minerals, liquids, gasses, and other materials for the use of mankind.
(3) "Professional geologist" is a person who is a graduate of an institution of higher education which is accredited by a regional or national accrediting agency, with a minimum of thirty semester (forty-five quarter) hours of undergraduate or graduate work in a field of geology and whose post baccalaureate training has been in the field of geology with a specific record of an additional five years of geological experience to include no more than two years of graduate work.
34-1-202. Reports containing geologic information. Any report required by law or by rule and regulation, and prepared as a result of or based on a geologic study or on geologic data, or which contains information relating to geology, as defined in section 34-1-201 (2), and which is to be presented to or is prepared for any state agency, political subdivision of the state, or recognized state or local board or commission, shall be prepared or approved by a professional geologist, as defined in section 34-1-201 (3).
For more information please see:
The NATIONAL ASSOCIATION OF STATE BOARDS OF GEOLOGY