Supreme Judicial Court Chief Justice Margaret Marshall publicly apologized yesterday for making an off-the-cuff and - politically speaking, at least - off-color joke about “red states” during a commencement speech in May. The Judicial Conduct Commission investigated Marshall after a complaint was made by an unidentified Bay State resident “intimately involved in the political process,” said one source familiar with the probe. Marshall has become a controversial political figure, particularly with the anti-gay-marriage movement, because she authored the SJC’s ruling legalizing homosexual marriage in 2003. JCC executive director Jill Pearson said she could not divulge the name of the complainant,...