Examine source code of Gritty orange wall

{
  "theme": {
    "images": {
      "theme_frame": "Grittyorange.jpeg"
    },
    "colors": {
      "frame": "#969696",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "Gritty orange wall",
  "manifest_version": 2,
  "description": "This is a nice, gritty orange wall theme for your Firefox browser."
}