Everybody above is correct , @jsowalsk ! Wear anything or nothing as your mood dictates. Colorado is a rather progressive state, so "nothing" may really be an option.
My advice is to keep it casual, and especially in regards to shoes. Since most presenters are also attendees, you will not want to spend the rest of your day slogging around in high heels, or even dress flats! I have a cute story from two InstCons ago where I was riding the shuttle back up to the Conference Center after breakfast listening to one young lady dressed to the nines (including four-inch spike heels) bitterly and loudly complaining about the eating location, and how could Instructure possibly expect folks to walk around a wet grassy field to get breakfast. Obviously she was expecting a different conference along the lines of those held at a major hotel/conference center where the only traveling you would do is up and down an elevator.
Kelley