Examine source code of Dark Theme Classic

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "dark theme glossy ",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-002-609370e89a219e0548ac5ef6b4a7dd2e.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(75, 75, 75)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(140, 140, 140)",
      "toolbar_field": "rgb(0, 0, 0)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(0, 0, 0)",
      "popup": "rgb(0, 0, 0)",
      "popup_text": "rgb(140, 140, 140)",
      "tab_loading": "rgb(0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{f6c1d542-08cc-4f53-8235-083ec4b00f60}"
    }
  }
}