chrome.runtime.onInstalled.addListener(function() {
  chrome.storage.sync.set({ color: "#3aa757" }, function() {
    console.log("The color is green.");
  });
  chrome.declarativeContent.onPageChanged.removeRules(undefined, function() {
    chrome.declarativeContent.onPageChanged.addRules([
      {
        conditions: [
          new chrome.declarativeContent.PageStateMatcher({
            pageUrl: {hostEquals: 'developer.chrome.com'}
          })
        ],
        actions: [
          new chrome.declarativeContent.ShowPageAction()
        ]
      }
    ])
  })
})