Examine source code of testNotebookTheme

{
  "description": "Theme using a PNG as the theme_frame image, employing a faded edge. See https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Examples#themes",
  "manifest_version": 2,
  "name": "test",
  "version": "1.1",
  "homepage_url": "https://github.com/mdn/webextensions-examples/tree/master/themes/weta_fade",
  "theme": {
    "images": {
      "theme_frame": "test.png"
    },
    "colors": {
      "toolbar_text": "rgba(0, 0, 0, 0.75)",
      "sidebar_text": "rgba(254, 255, 181, 0.75)",
      "popup_text": "rgba(254, 255, 200, 0.75)",
      "tab_text": "rgba(0, 0, 0, 0.75)",
      "tab_background_text": "rgba(254, 255, 200, 0.75)",
      "icons": "rgba(0, 0, 0, 0.75)",
      "toolbar_field_text": "rgba(0, 0, 0, 0.75)",
      "ntp_text": "rgba(254, 255, 200, 0.75)",
      "toolbar_highlight_text": "",
      "sidebar_highlight_text": "",
      "popup_highlight_text": "",
      "toolbar_field_highlight_text": "",
      "toolbar": "rgba(254, 255, 200, 0.75)",
      "sidebar": "rgba(128, 128, 128, 0.75)",
      "frame": "rgba(136, 42, 29, 1)",
      "popup": "rgba(136, 42, 29, 0.75)",
      "tab_selected": "rgba(254, 255, 200, 0.75)",
      "toolbar_field": "rgba(136, 42, 29, 0.75)",
      "ntp_background": "rgba(128, 128, 128, 0.75)",
      "sidebar_highlight": "",
      "popup_highlight": "",
      "toolbar_field_highlight": "",
      "frame_inactive": "",
      "button_background_active": "",
      "icons_attention": "",
      "tab_line": "",
      "tab_loading": "",
      "button_background_hover": "",
      "sidebar_border": "rgba(255, 255, 255, 0)",
      "popup_border": "rgba(255, 255, 255, 0)",
      "toolbar_field_border": "rgba(0, 0, 0, 0)",
      "toolbar_bottom_separator": "",
      "toolbar_top_separator": "",
      "toolbar_vertical_separator": "",
      "toolbar_field_focus": "",
      "toolbar_field_text_focus": "",
      "toolbar_field_border_focus": ""
    },
    "properties": {}
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ed2d240b-56a9-45db-af1b-0762bc029fc2}"
    }
  }
}