Examine source code of Simple Dark

{
  "manifest_version": 2,
  "version": "3.0",
  "name": "Simple Dark",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(16, 16, 16)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(16, 16, 16)",
      "tab_background_text": "rgb(238, 238, 238)",
      "toolbar_field": "rgb(32, 32, 32)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(40, 255, 255)",
      "popup": "rgb(16, 16, 16)",
      "popup_text": "rgb(238, 238, 238)",
      "tab_loading": "rgb(40, 255, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{02be1381-a3d9-460c-b209-5b39b42e2b30}"
    }
  }
}