Examine source code of flat-plat

{
  "theme": {
    "images": {
      "theme_frame": "header.png"
    },
    "colors": {
      "frame": "#455a64",
      "tab_background_text": "#ffffff"
    }
  },
  "version": "2.0",
  "name": "flat-plat",
  "manifest_version": 2,
  "description": "Based on the flat-plat GTK3 theme: <a rel=\"nofollow\" href=\"https://outgoing.prod.mozaws.net/v1/b448d729ef8f3b7226d5f584d792702a10f8b941f4358c3c5b0cc635afc1f079/https%3A//github.com/nana-4/Flat-Plat\">https://github.com/nana-4/Flat-Plat</a>"
}