STAFF PICK: Is he black or is he white? Is he gay or is he straight? Controversy, indeed. In addition to delicious ribs and roast beef, Jack's Barbecue boasts perhaps the most perplexing sign in Tucson, if not the Southwest proper. By day, the character on the store's main sign (presumably Jack) is distinctly Anglo. By night, however, he is African-American. This is not simply a trick of lighting, as some claim; the translation, albeit subtle, is truly unsettling, and has caused a number of motorists over the years to actually slow down to the posted speed limit. The question, of course, is: Why? What does this biracial mascot portend? Of what significance is this transformation? A random survey of three or four Tucsonans waiting in line for a movie at El Con revealed little agreement as to the underlying meaning of the Jack's sign, although all agreed that it was quite hot that day.