It’s looking increasingly likely that the next mayor of Boston will be a female person of color — but for years, the city’s inability or unwillingness to elect anyone other than white men has been a defining trait. In Denver, meanwhile, which resembles Boston in several respects, three of the last four mayors have been people of color. So what gives? Nearly a decade ago, GBH News senior editor Ken Cooper — who grew up in Denver, but has called Boston home for years — offered some answers in an article published by UMass Boston’s Trotter Review. He joined Peter Kadzis and Adam Reilly to recap and update his findings — and to offer some thoughts on why, finally, Boston seems poised to change its electoral habits.