Examine source code of Wally Darling @:)

{
  "name": "Welcome Home @:)",
  "manifest_version": 2,
  "version": "1.0",
  "theme": {
    "images": {
      "theme_frame": "19.png"
    },
    "colors": {
      "frame": "rgba(204, 94, 34, 1)",
      "tab_background_text": "rgba(184, 2, 2, 1)",
      "toolbar": "rgba(250, 151, 53, 1)",
      "bookmark_text": "rgba(79, 28, 1, 1)",
      "toolbar_field": "rgba(247, 219, 195, 1)",
      "toolbar_field_text": "rgba(255, 121, 3, 1)",
      "tab_line": "rgba(201, 2, 2, 1)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{678ebd81-4bb0-4726-9e87-b95a0e2bca07}"
    }
  }
}