Examine source code of Embrace the Gray

{
  "manifest_version": 2,
  "version": "1.0",
  "name": "Dark Gray",
  "theme": {
    "images": {
      "additional_backgrounds": [
        "images/bg-009-f069b97f439938a011297c84464f0df6.svg"
      ]
    },
    "properties": {
      "additional_backgrounds_alignment": [
        "top"
      ],
      "additional_backgrounds_tiling": [
        "repeat"
      ]
    },
    "colors": {
      "toolbar": "rgb(51, 69, 72)",
      "toolbar_text": "rgb(255, 255, 255)",
      "frame": "rgb(61, 84, 87)",
      "tab_background_text": "rgb(255, 255, 255)",
      "toolbar_field": "rgb(61, 84, 87)",
      "toolbar_field_text": "rgb(255, 255, 255)",
      "tab_line": "rgb(255, 255, 255)",
      "popup": "rgb(61, 84, 87)",
      "popup_text": "rgb(255, 255, 255)",
      "tab_loading": "rgb(255, 255, 255)"
    }
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{7709487c-2999-4d09-9c09-265040946a66}"
    }
  }
}