Comedian Stephen Colbert delivers the commencement address at Wake Forest University. Referring to the graduates' mortar boards, he said: 'Everyone has a black and gold tassel. Or is it blue and white? Grandparents, this was the issue that divided a generation ... You had the Vietnam war. Your grandchildren had an ambiguously coloured Tumblr post.' Colbert will take over from David Letterman as host of the Late Show in December