Examine source code of gruber-darker

{
  "manifest_version": 2,
  "version": "1.1",
  "name": "gruber-darker",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(40, 40, 40)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(24, 24, 24)",
      "tab_background_text": "rgb(72, 72, 72)",
      "toolbar_field": "rgb(72, 72, 72)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(40, 40, 40)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(150, 166, 200)",
      "button_background_hover": "rgb(72, 72, 72)",
      "frame_inactive": "rgb(24, 24, 24)",
      "icons": "rgb(255, 255, 255)",
      "popup_border": "rgb(40, 40, 40)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{2eb09573-f92c-414b-9fed-fd7ebd412da2}"
    }
  }
}