Examine source code of FF Windows Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Default Dark",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(43, 42, 51)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(28, 27, 34)",
      "tab_background_text": "rgb(189, 187, 201)",
      "toolbar_field": "rgb(66, 65, 77)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(66, 65, 77)",
      "popup": "rgb(66, 65, 77)",
      "popup_text": "rgb(255, 255, 255)",
      "button_background_active": "rgb(83, 81, 97)",
      "button_background_hover": "rgb(66, 65, 77)",
      "frame_inactive": "rgb(35, 34, 41)",
      "popup_border": "rgb(83, 81, 97)",
      "popup_highlight": "rgba(101, 123, 105, 0.6)",
      "sidebar_highlight": "rgba(101, 123, 105, 0.6)",
      "sidebar": "rgb(43, 42, 51)",
      "tab_loading": "rgb(101, 123, 105)",
      "tab_selected": "rgb(66, 65, 77)",
      "toolbar_field_highlight": "rgba(101, 123, 105, 0.6)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{26402350-0587-41d4-ac4b-6dd8fe76ea09}"
    }
  }
}