Examine source code of Dark theme (jadin.me)

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Simple Dark",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(23, 23, 23)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(43, 43, 43)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(23, 23, 23)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(23, 23, 23)",
      "popup": "rgb(23, 23, 23)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(23, 23, 23)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{5af8e81c-5d61-4c68-9b5d-7e36328c9801}"
    }
  }
}