My research suggests that you are right in your selection of Colorado as one of the safer places of refuge in the USA when the axis shift takes places. There are just a few points that you should keep in mind. You have already mentioned one of them-the presence of calderas. Most dormant calderas can only be located by a trained geologist, so you will have to make sure that the site of your underground bunker is chosen with the greatest of care.
Secondly, I hope that you realize that when the tectonic plates begin to grind against each other during the shift, all the calderas and volcanoes, dormant and active, are going to explode with incredible force, spewing forth massive amounts of volcanic ash. It has been calculated that when the Yellowstone caldera explodes, it is going to contaminate the air over most of the US. Just think of the fact that there are numerous calderas in North America as well as all over the rest of the world.
What I am trying to point out is that the air over the entire planet is going to be filled with swirling masses of toxic volcanic ash. If you breathe this stuff, it settles in the lungs, combines with the moisture there to form a hard cement-like material that suffocates you. You will have to install a first rate air filtration system in your bunker or else you will die.
I hope you are not one of those people planning to survive by hunting after the shift. Hunting will be almost impossible since the vast majority of animals will have been killed by the effects of the volcanic ash. The recent volcano eruption on the Caribbean island of Montserrat shows very clearly that it is the volcanic ash that kills most people. Islanders who successfully escaped the lava were killed by the ash.
Finally, once it becomes known that Colorado is one of the safer sites in the US, the place is going to be swarming with "refugees" from other parts of North America desperately seeking safety. Before this happens, you are going to have to make sure that your bunker, reinforced with concrete and steel, has been built, that a latrine and air-filtration system have been established, that you have enough food and equipment to last for eighteen months and that you have the necessities to restart life for you and your family.