Examine source code of gnome-engineer-dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "gnome-engineer",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-026-829b05416f823e170310e7c826ad1bec.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(28, 28, 28)",
      "toolbar_text": "rgb(197, 207, 227)",
      "frame": "rgb(48, 48, 48)",
      "tab_background_text": "rgb(199, 199, 199)",
      "toolbar_field": "rgb(28, 28, 28)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(87, 117, 117)",
      "popup": "rgb(27, 40, 45)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(87, 117, 117)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e050c354-45d7-4961-ae7e-c7f013d1b73d}"
    }
  }
}