Examine source code of Firefox 4 Colorful

{
  "theme": {
    "images": {
      "theme_frame": "Header_firefox1.png"
    },
    "colors": {
      "frame": "#ffffff",
      "tab_background_text": "#000"
    }
  },
  "version": "2.0",
  "name": "Firefox 4 Colorful",
  "manifest_version": 2,
  "description": "This was designed for Firefox 4. The white semi-opaque effect should fit your statusbar."
}