CBS has done this before, with this vintage, beloved CBS series, and with The Dick Van Dyke Show: Take a pair of classic episodes, colorize them by new computer techniques, and show them in prime time. And tonight, CBS is doing it again, showing a pair of Lucille Ball’s later I Love Lucy “Hollywood” episode. The classic one, truly, is the one with Lucy and Harpo Marx, recreating the seminal broken-mirror scene from the riotous Marx Brothers movie Duck Soup. I used to be totally