Examine source code of Vivaldi - Subtle

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Vivaldi - Subtle",
  "theme": {
    "images": {},
    "properties": {},
    "colors": {
      "toolbar": "rgb(246, 246, 246)",
      "toolbar_text": "rgb(51, 51, 51)",
      "frame": "rgb(204, 204, 204)",
      "tab_background_text": "rgb(51, 51, 51)",
      "toolbar_field": "rgb(255, 255, 255)",
      "toolbar_field_text": "rgb(51, 51, 51)",
      "tab_line": "rgba(51, 51, 51, 0.19)",
      "popup": "rgb(246, 246, 246)",
      "popup_text": "rgb(51, 51, 51)",
      "tab_loading": "rgba(51, 51, 51, 0.19)"
    }
  }
}