Bob Ross died on July 4, 1995 — a touching coda for the landscape artist whose PBS collection, “The Joy of Painting,” freed the art world from its stuffiness and designed it accessible to all people. The legacy of Ross, who would have turned seventy eight in October, is inarguable. His reassuring, calming voice, the “happy very little trees” he painted on Tv set and even his expansive afro reworked “The Joy of Painting” into an legendary pop-lifestyle phenomenon that is aired somewhere in the US — just about every one working day — due to the fact its premiere…