Examine source code of Simple Fox (Charcoal)

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#222222",
      "tab_background_text": "#AEE9D1"
    }
  },
  "version": "2.0",
  "name": "Simple Fox (Charcoal)",
  "manifest_version": 2,
  "description": "Dark, almost black background with simple Firefox Logo."
}