[The series and its rules are explained here, where you will also find links to the songs for the other states.]
6:1. Ft Worth Blues: 'But Colorado's always clean and healing'. (1, 2.)
6:2. Rocky Mountain High: 'It's a Colorado Rocky Mountain High'. (1, 2, 3.)
6:3. Colorado Christmas: 'The closest thing to heaven on this planet anywhere / Is a quiet Christmas morning in the Colorado snow'. (1, 2.)
6:4. Someday Soon: 'Comes from down in southern Colorado'. (1, 2, 3 a minute and a half in, 4.)
6:5. Get Out Of Denver: 'We're staring at a Colorado state policeman trooper cat'. (1, 2.)
6:6. Colorado Girl: 'That lovin' Colorado girl of mine'. (1, 2.)
6:7. Old Dominion: 'So grow up, Colorado'. (1.)
6:8. Rhode Island Is Famous For You: 'Grand canyons come from Colorado'. (1, 2, 3, 4.)
6:9. Man Of Constant Sorrow: 'I'll say goodbye to Colorado'. (1, 2, 3, 4.)
6:10. California Zephyr: 'Colorado and Nevada'. (1, 2.)
6:11. Colorado: 'If I had a wagon, I would go to Colorado'. (1.)
6:12. Colorado: 'Guess she was afraid of bein' alone in Colorado'. (1, 2.)
6:13. West Texas Wind: 'And Colorado's more than eight hundred miles away'. (1.)
6:14. Colorado Country Morning: 'I've got a Colorado country morning and a Denver woman on my mind'. (1, 2.)
6:15. I Guess He'd Rather Be in Colorado. (1, 2, 3.)
6:16. Wanted Man: 'I might be in Colorado'. (1, 2, 3.)
6:17. Cadillac Ranch: 'Drivin' all alone in the Colorado night'. (1.)
6:18. If It Ain't Dixie: 'Oh I love those Colorado Rockies'. (1.)
6:19. I've Been Everywhere: 'Pittsburgh, Parkersburg, Gravellburg, Colorado'. (1, 2, 3.)
6:20. The Brothers: 'Momma, is Joe still driving them old nails out in Colorado'. (1, 2.)