Examine source code of backgroundf

{
  "name": "background",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "background.gif"
    },
    "colors": {
      "frame": "rgba(0, 0, 0, 1)",
      "tab_background_text": "rgba(119, 40, 199, 1)",
      "toolbar": "rgba(31, 31, 31, 0.38)",
      "bookmark_text": "rgba(119, 40, 199, 1)",
      "toolbar_field": "rgba(0, 0, 0, 1)",
      "toolbar_field_text": "rgba(119, 40, 199, 1)",
      "tab_line": "rgba(121, 55, 196, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7d9f6a65-3829-4e81-8cd5-7c29a9d0d499}"
    }
  }
}