Examine source code of Facebook - simple colors.

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#000000",
      "tab_background_text": "#000000"
    }
  },
  "version": "2.0",
  "name": "Facebook - simple colors.",
  "manifest_version": 2,
  "description": "This theme is facebook theme for mozilla firefox browser. dveloped by veer from delhi, during his project work."
}