If you're asking for a lawyer's opinion, might put this question in the "Ask the Lawyer" section. Other than that, I would agree with Sammyboy - don't let folks know about the firearm. That means not talking about it with work folks. Another thought is the possibility of parking in another spot outside the employee lot but I don't know it that is feasible.
Obviously I would keep the vehicle locked and suggest having the weapon in a small gunsafe under a seat or possibly in a console - that way you can argue that it was unavailable to the average person.
Not sure what kind of company you work for, but I'm guessing the chances of them searching all vehicles in the parking area is slim. Other than keeping a low profile and not causing reason for a search, I'm guessing you just take your chances unless Colorado has some sort of parking lot bill like Texas.