Be nice to have state registration stats. Can you find those?
This?
http://www.sos.state.co.us/pubs/elections/VoterRegNumbers/VoterRegNumbers.html
To get 2012 stats change ‘2016’ in the url to ‘2012’ ex:
http://www.sos.state.co.us/pubs/elections/VoterRegNumbers/2012/September/VotersByPartyStatus.pdf