Table:
text: United States House of Representatives elections, 2006
Colorado
Colorado
District Incumbent Party First_elected Results
Colorado 1 Diana DeGette Democratic 1996 Re-elected
Colorado 2 Mark Udall Democratic 1998 Re-elected
Colorado 3 John Salazar Democratic 2004 Re-elected
Colorado 4 Marilyn Musgrave Republican 2002 Re-elected
Colorado 5 Joel Hefley Republican 1986 Retired Republican hold
Colorado 6 Tom Tancredo Republican 1998 Re-elected
Colorado 7 Bob Beauprez Republican 2002 Retired to run for Governor Democratic gain

Question: In which district is the incumbent Republican and the incumbent retired to run for the Democratic win of governor in the 2006 United States House of Representatives election in Colorado?