Examine source code of HOTWords

{
  "theme": {
    "images": {
      "theme_frame": "top.png"
    },
    "colors": {
      "frame": "#cf6b00",
      "tab_background_text": "#1c1515"
    }
  },
  "version": "2.0",
  "name": "HOTWords",
  "manifest_version": 2,
  "description": "HOTWords template for Firefox"
}