Examine source code of FreeFlight

{
  "theme": {
    "images": {
      "theme_frame": "snowboarding.jpg"
    },
    "colors": {
      "frame": "#7a1d1d",
      "tab_background_text": "#1a3580"
    }
  },
  "version": "2.0",
  "name": "FreeFlight",
  "manifest_version": 2,
  "description": "Alpine theme, inspired by the absolute freedom of snowboarding through virgin snow."
}