Examine source code of At the Lake...

{
  "name": "Lake view UHD Size",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "lakeview.png"
    },
    "colors": {
      "frame": "rgba(255, 255, 255, 1)",
      "tab_background_text": "rgba(255, 255, 255, 1)",
      "toolbar": "rgba(226, 181, 0, 0.66)",
      "bookmark_text": "rgba(255, 255, 255, 1)",
      "toolbar_field": "rgba(96, 92, 49, 0.71)",
      "toolbar_field_text": "rgba(255, 255, 255, 1)",
      "tab_line": "rgba(255, 255, 255, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{a91c896b-f480-4b62-bf7c-750c5308e2ce}"
    }
  }
}