Examine source code of Fireworks

{
  "theme": {
    "images": {
      "theme_frame": "Feuerwerk_0007_Header.jpg"
    },
    "colors": {
      "frame": "#fcfcfc",
      "tab_background_text": "#fafafa"
    }
  },
  "version": "2.0",
  "name": "Fireworks",
  "manifest_version": 2,
  "description": "Fireworks for your Firefox created by Strucky"
}