The issue isn't uniforms. If a perp shoots a security guard and uses the excuse that he "thought" it was a cop, he's still a malicious thug and cop-killer due to the fact that it's a premeditated "hate" crime. And if a punk DOESN'T commit an act of vandalism because he thought the bystander was a cop when he's really a security guard, isn't that the idea behind having security guards?
The issue is "impersonation" (if the security guard REPRESENTS himself as a cop - or that punk with the jacket and lightbar).
But the issue in TULSA (those outside the area may not get the news on this one) is that the current Mayor is running for re-election - and that he's NO FRIEND OF THE POLICE Department AND he has a terrible reputation concerning the crime rate. There's little chance he could get a real cop to stand behind his campaign commercial, let along "perform" in it. So the idiosyncracy of "green" uniforms would have prevented him from easily "renting" an actor to play a TPD officer, whereas the switch to a common "blue" one meant he didn't even have to go to the costume shop - just swing by a local mall or apartment complex.