"When Matisse dies," Pablo Picasso remarked in the 1950s, "Chagall will be the only painter left who understands what color really is." As a pioneer of modernism and one of the greatest figurative artists of the twentieth century, Marc Chagall achieved fame and fortune, and over the course of a long career created some of the best-known and most-loved paintings of our time. Yet behind this triumph lay struggle, heartbreak, bitterness, frustration,...