I went back and re-read your question, and think I slightly misread it.
This is, I believe, the crux of your question:
(B) Subparagraph (A) does not apply to the possession of a firearm-
(ii) if the individual possessing the firearm is licensed to do so by the State in which the school zone is located or a political subdivision of the State, and the law of the State or political subdivision requires that, before an individual obtains such a license, the law enforcement authorities of the State or political subdivision verify that the individual is qualified under law to receive the license;
Looking between that, and the state CRS, I'd say that it's still technically illegal, even if concealed - again, unless that ground is private property. This might be one case where I'd advocate "conceal it and just be quick about your task".
But this part bears noting, as well:
(ii) if the individual possessing the firearm is licensed to do so by the State in which the school zone is located or a political subdivision of the State, and the law of the State or political subdivision requires that, before an individual obtains such a license, the law enforcement authorities of the State or political subdivision verify that the individual is qualified under law to receive the license;
I can't find a link to say Colorado's CHP is appropriate for a "license" in this case, as the CRS only refers to the real property, not the zone. I'd honestly suggest asking the county Sheriff or an LEO that you trust to give a straight answer.
Good question, though. I'm training with a police firearms instructor this weekend, and I also know the local POST chief instructor, so I may ask them both.