Even though green beer will flow freely today, one of the biggest drinking holidays of the year, few beer connoisseurs understand its appeal. "I don't knock people who drink green beer," says Kieran Folliard, who owns four Irish pubs — Liffey in St. Paul, Cooper in St. Louis Park and Kieran's and the Local in Minneapolis. "But to be quite honest, I wouldn't drink it unless I was stuck in the desert and it was the only thing around." Sean O'Byrne, who opened Great Waters Brewing Co. 15 years ago today, won't touch the stuff for any reason. "Never have,...