Examine source code of horizon_sunset

{
  "theme": {
    "images": {
      "theme_frame": "horizon_header.jpg"
    },
    "colors": {
      "frame": "#050505",
      "tab_background_text": "#f7f4f4"
    }
  },
  "version": "2.0",
  "name": "horizon_sunset",
  "manifest_version": 2,
  "description": "Sunset over the prairie with some farmhouses."
}