Examine source code of sapi-cow

{
  "theme": {
    "images": {
      "theme_frame": "firefox.jpg"
    },
    "colors": {
      "frame": "#080a69",
      "tab_background_text": "#15eddf"
    }
  },
  "version": "2.0",
  "name": "sapi-cow",
  "manifest_version": 2
}