Examine source code of Simple Dark for Firefox

{
  "manifest_version": 2,
  "version": "1.4",
  "name": "Simple Dark",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(56, 56, 61)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(12, 12, 13)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(33, 33, 33)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgba(57, 57, 57, 0)",
      "popup": "rgb(56, 56, 61)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(82, 82, 82)",
      "button_background_hover": "rgb(72, 72, 72)",
      "frame_inactive": "rgb(78, 78, 78)",
      "icons": "rgb(237, 237, 237)",
      "ntp_text": "rgb(255, 255, 255)",
      "popup_border": "rgb(85, 85, 85)",
      "popup_highlight_text": "rgb(255, 255, 255)",
      "popup_highlight": "rgb(91, 95, 97)",
      "sidebar_highlight_text": "rgb(255, 255, 255)",
      "sidebar_text": "rgb(255, 255, 255)",
      "tab_loading": "rgba(255, 255, 255, 0)",
      "toolbar_field_focus": "rgb(33, 33, 33)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{8394550a-7177-4744-a3e1-8e9eb6873850}"
    }
  }
}