I did this exact thing a few years ago and haven't had any issues, but I'm in ND.  It took about a year for the mice smell in the quonset that the seed used to be kept in to go away.  After the seed was moved into the conex I had it fumigated to make sure everything was dead.  Being you are in CO, shade and ventilation should be good enough to keep temps down.  One option to create some shade would be to weld on a canopy a few feet above the top of the conex.