Peter Max, whose colorful, psychedelic pop art expressed the optimism of the “flower power” movement of the 1960s and graced everything from postage stamps to a cruise ship, has died at 88, his son said in a written statement Wednesday.Max died on Monday, the statement said. No cause was given. Max began his career in graphic design in the 1960s, and his swirly, colorful, instantly recognizable designs epitomized the era’s “flower power” art. But thanks to his prolific output and fun, accessible style, Max’s work remained well known and popular well into the 21st century. Max was the official artist...