Colorado
(at least 5,000 signatures from eligible electors who have not signed a petition for any other candidate for the same office)
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentQuals.pdf
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentPetitionAcceptance.pdf
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentElectorsAccept.pdf
(at least 5,000 signatures from eligible electors who have not signed a petition for any other candidate for the same office)
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentQuals.pdf
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentPetitionAcceptance.pdf
http://www.sos.state.co.us/pubs/elections/Candidates/files/PresidentElectorsAccept.pdf