Examine source code of FirefoxDefaultGray

{
  "theme": {
    "images": {
      "theme_frame": "p1.png"
    },
    "colors": {
      "frame": "rgba(229,230,232,1)",
      "tab_background_text": "#2e2d2d"
    }
  },
  "version": "2.0",
  "name": "FirefoxDefaultGray",
  "manifest_version": 2,
  "description": "just a simple gray background, but footer image is the samo color as the bottom of the header so some extensions i am using dont look  incomplete"
}