Examine source code of Thunderbird Carbon dark

{
  "theme": {
    "images": {
      "theme_frame": "thunderbird-carbon001a.jpg"
    },
    "colors": {
      "frame": "#c2b4b4",
      "tab_background_text": "#ede6e6"
    }
  },
  "version": "2.0",
  "name": "Thunderbird Carbon dark",
  "manifest_version": 2,
  "description": "Thunderbird Carbon dark"
}