Examine source code of Bluebells

{
  "name": "Bluebells",
  "manifest_version": 2,
  "version": "3.0",
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "toolbar": "rgba(0, 0, 0, 0)",
      "toolbar_field": "rgba(0, 0, 0, 0)",
      "frame": "#ffffff",
      "tab_background_text": "#452b94"
    }
  }
}