Examine source code of Red Line

{
  "theme": {
    "images": {
      "theme_frame": "Browser_head_Versuch_3.png"
    },
    "colors": {
      "frame": "#a6a3a3",
      "tab_background_text": "#fcfcfc"
    }
  },
  "version": "2.0",
  "name": "Red Line",
  "manifest_version": 2
}