Examine source code of xmas theme

{
  "theme": {
    "images": {
      "theme_frame": "xmas-2.jpg"
    },
    "colors": {
      "frame": "#4f4f4f",
      "tab_background_text": "#0a0a0a"
    }
  },
  "version": "2.0",
  "name": "xmas theme",
  "manifest_version": 2
}