If the Chelsea bomber had packed his second pressure-cooker IED in a less eye-catching bag, two men might not have removed it—and it might have killed dozens at an open-air restaurant. Had the bomber chosen a simple black or solid hue wheeled suitcase, the two men who happened by might not have even noticed it sitting on a dimly lit patch of pavement on the uptown side of West 27th Street. “They might have just walked right on by,” a high-ranking cop said on Monday. But the wheelie bag the bomber left had an eye-catching pattern whose multi colors included...