Examine source code of Blue World Map

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#76807d",
      "tab_background_text": "#14255c"
    }
  },
  "version": "2.0",
  "name": "Blue World Map",
  "manifest_version": 2,
  "description": "A Blue World map theme to make your Firefox windows look more dark and cool the next time you open it."
}