Stephen Colbert has expressed regret about making cruel jokes towards Princess Kate. The US talk show host appeared on his show, The Late Show With Stephen Colbert, on Monday evening to address the Princess of Wales’s cancer diagnosis. Last week, Kate, 42, recorded a video message at Adelaide Cottage to announce she was undergoing a course of preventative chemotherapy for an unspecified form of cancer. This video was released on Friday evening after weeks of speculation online regarding Kate’s whereabouts. During her emotional video, the princess said: “In January, I underwent major abdominal …