Welcome to OCDO!
In Colorado, if your pistol were not visible due to it being covered by the smock at a barber's shop, it would be considered concealed and therefore illegal without a permit. It phrases it as "knowingly and unlawfully" (CRS 18-12-105); since you would "knowingly" be allowing your gun to be covered, it would be the same as intentionally concealing it under your shirt. Thankfully, you don't have to worry about that in your car, with it being hidden between the seat and center console, etc, but on foot it's one of the most irritating things about not having a CHP in CO. Sorry it couldn't be a better answer!