Irving Berlin’s White Christmas is a timeless tale of joy and goodwill which will be opening December 2 at the Colonial Theatre in Pittsfield. We get a preview of the Berkshire Theatre Group production this morning. Full of dancing, laughter and some of the greatest songs ever written, the dazzling score features, “Blue Skies,” “Count Your Blessings,” “I Love a Piano,” “How Deep is the Ocean?” and of course the unforgettable title song, “White Christmas.” To tell us more, we welcome the four lead actors from the show, Mike Wartella, Michael Starr, and Claire and Alanna Saunders.