Some of the maps I have found showing each state's status on open carry of a handgun are a bit out of date.
I went to the most current sources I could find and produced an updated map to show just how prevalent laws allowing open carry really are.
A few notes: California is an anomaly. The state used to permit open carry of a loaded handgun without a permit. That was changed after the Black Panthers marched through the Capitol in Sacramento back in 1967. The new law said it was okay to openly carry an unloaded handgun without a permit. You could have the ammunition elsewhere on your person but not loaded in the gun. That lasted until the Open Carry movement in California started meeting at Starbucks while carrying their unloaded guns. Police complained that calls about the group were interfering with other work and California banned open carry without a license altogether. Given the obstacles to getting a carry license in California, it should have been a statewide ban. However, some California sheriffs are more willing to issue, so carry in those areas is allowed. So California is orange instead of red (by the way, the colors have nothing to do with politics).
Utah permits open carry of a loaded firearm with a state-issued permit. However, it allows open carry of an unloaded firearm without a permit. The quirk is that Utah considers a gun to be unloaded if there is not a round in the chamber. This means one can carry a pistol with a full magazine inserted but as long as the slide has not been racked to load a cartridge in the chamber, it's okay to open carry.
Colorado, Delaware and Pennsylvania allow unlicensed open carry except in the cities of Boulder and Denver, Dover, and Philadelphia, respectively. Nebraska allows it except in Omaha, where one must get a special permit from the city. Some local governments in North Carolina restrict open carry within the city limits.
Seven states allow unlicensed open carry as long as one is on foot. To carry in a car requires a permit.
So 28 states currently allow generally unlicensed open carry. Another 16 allow it with a state-issued license. Five states and the District of Columbia (too small to show on map) either forbid it or heavily restrict it.