Examine source code of Beautiful Opera Dark

{
  "manifest_version": 2,
  "version": "2.4",
  "name": "Beautiful Opera Dark",
  "description": "Tema al estilo Opera para Firefox.",
  "icons": {
    "32": "icon-32.png"
  },
  "theme": {
    "colors": {
      "frame": "#333334",
      "tab_background_text": "#eeeeee",
      "frame_inactive": "#3a3a3b",
      "toolbar": "#5a5b5c",
      "toolbar_field": "#2d2e2e",
      "toolbar_field_text": "#d3d8db",
      "toolbar_top_separator": "#252626",
      "toolbar_bottom_separator": "#252626",
      "toolbar_field_border": "#737475",
      "toolbar_field_border_focus": "#757575",
      "toolbar_field_highlight": "#5d5d5f",
      "toolbar_field_highlight_text": "#ffffff",
      "toolbar_field_text_focus": "#e5e5e6",
      "toolbar_vertical_separator": "#BBBBBB",
      "button_background_hover": "#505050",
      "button_background_active": "#404040",
      "icons": "#e9edee",
      "icons_attention": "#e2e5e7",
      "ntp_background": "#2d2e2e",
      "ntp_text": "#d3d8db",
      "ntp_card_background": "#424343",
      "popup": "#2d2e2eFD",
      "popup_text": "#d3d8db",
      "popup_border": "#99999980",
      "popup_highlight": "#484849",
      "sidebar": "#2d2e2e",
      "sidebar_text": "#d3d8db",
      "sidebar_border": "#99999980",
      "sidebar_highlight": "#191a1a",
      "sidebar_highlight_text": "#EEEEEE",
      "tab_line": "#5a5b5c",
      "tab_loading": "#ffffff",
      "tab_loading_inactive": "#ffffff",
      "tab_selected": "#5a5b5c",
      "tab_background_separator": "#6b6b6c",
      "tab_text": "#ffffff"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{efba1eb4-98ce-4910-9602-64e141274239}"
    }
  }
}