Examine source code of digital firefox.......

{
  "theme": {
    "images": {
      "theme_frame": "Persona_Header_LABS.jpg"
    },
    "colors": {
      "frame": "#ffff00",
      "tab_background_text": "#ffff00"
    }
  },
  "version": "2.0",
  "name": "digital firefox.......",
  "manifest_version": 2
}