WASHINGTON — The White House warned Tuesday of a “revolution” of computer-generated threats to the U.S. stoked by growing cyber aggression by traditional U.S. foes like Russia and North Korea, and issued a color-coded response plan for the federal government to use after major cyberattacks. Lisa Monaco, President Barack Obama’s homeland security and counterterrorism adviser, said while Russia and China grow “more assertive and sophisticated” online, Iran has attacked U.S.