Examine source code of Simply_Dark

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Simply Dark",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-015-79a105bb546d3dfdd686392cf3ad1f57.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(17, 17, 17)",
      "toolbar_text": "rgb(251, 251, 251)",
      "frame": "rgb(0, 0, 0)",
      "tab_background_text": "rgb(214, 214, 214)",
      "toolbar_field": "rgb(3, 3, 3)",
      "toolbar_field_text": "rgb(214, 214, 214)",
      "tab_line": "rgb(0, 0, 0)",
      "popup": "rgb(7, 7, 7)",
      "popup_text": "rgb(255, 255, 255)",
      "sidebar": "rgb(7, 7, 7)",
      "tab_loading": "rgb(0, 0, 0)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{ba87c3df-0a51-45c1-94d6-ebc4f36431c2}"
    }
  }
}