What I learned from the military, a gas mask! Average person can go 30 days with no food, 3 days with no water, 3 minutes with no air. In case of a nuclear war, the air will be contaminated with radioactive fallout. Breathe it in and you are doomed. The gas mask will also protect you from noxious gases, tear gas for example.
I also have a Eurami geiger counter, it is solid state and the battery lasts ten years.
Colorado is a huge military target, but also has the advantage of you being able to hide out in rugged remote areas. Backpack, sleeping bag, and the ability to hunt and fish might mean the difference between life and death in a worse case scenario. Don't count on the Government to protect you, you have to protect your self.
If you are unfamiliar with survival techniques, try buying a book on survival such as a military manual or the SAS Survival manual.
Go camping and practice! Educate your self.